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Pushing an Airplane: Free Energy (For Someone)

02/01/2008 1:33 PM

There is always something new from Africa. (Or is it old?)

Instead of using a tractor to get a plane out of the parking space they use 12 labourers to push it out. (I think it was a 747) I wonder why they did not get Mr Iron man, he do it all by himself (with the help of only 2 labourers)

What can they do?

PS Gooz cards will be awarded for good and almost good answers.

PS1 I Don't want a reply that they should fix the draw-bar. The last one available also went missing overnight. I think a plane took of with it.

PS2 - More Gooz cards may be available (depending on the inflation rate in ZimLand. Just claim it if you want it.

PS3 - really nice graphics.

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#1

Re: Pushing an Airplane: Free Energy (For Someone)

02/01/2008 4:14 PM

Well Nepal Airlines fixes their jumbo jets by sacrificing goats to the gods... so why not hire a tribal mystic of some kind to move it by magic?

http://news.bbc.co.uk/1/hi/world/south_asia/6979292.stm

I am surprised it only took 12.. I am also a bit surprised at the number as I thought Africa used metric so I would have expected multiples of 10...

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#2
In reply to #1

Re: Pushing an Airplane: Free Energy (For Someone)

02/01/2008 5:10 PM

18 workers belonging to the Pen Pushers Union did not participate , they are not allowed to push planes.

For a 757 they should at least sacrifice a jumbo.

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#3

Re: Pushing an Airplane: Free Energy (For Someone)

02/01/2008 6:51 PM

Which bit do they push against? I assume it's the wheels (ie tyres), but just checking ...

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#4
In reply to #3

Re: Pushing an Airplane: Free Energy (For Someone)

02/02/2008 12:22 AM

Which bit do they push against? - I don't know - A new crowd were awarded the tender and it was their first day on the job.

I believe the hard part was getting it over the stays.

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#5

Re: Pushing an Airplane: Free Energy (For Someone)

02/02/2008 4:52 AM

If they did not push the wheels they must have been the tallest massai warriers I have ever seen as those wheels are the only bit normal people can reach.

I believe the nosecone is some 4 or 5 meter up, I am 6'5" and I hardly have to duck for those engines against which they would not allow you to push.

They would have been better off tieing some strong rope at the wheels either side under the wings and pull. That way you could have as many as you like or just the one strongest man of the world contender from Africa.

As the plane gets to the parking under its own power, why not build the parking lot on a slope? Just release the brake and off they go.

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#6
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Re: Pushing an Airplane: Free Energy (For Someone)

02/02/2008 5:34 AM

... that's kinda what I was thinking.

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#7
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Re: Pushing an Airplane: Free Energy (For Someone)

02/02/2008 6:41 AM

Good idea but it took years of education to get it on the level.

Would deflating the back wheels not help?

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#8
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Re: Pushing an Airplane: Free Energy (For Someone)

02/02/2008 6:58 AM

WHAAAAHAHAHA ha haha hmmm?


Maybe in south africa

To get this straight, you are kidding right? What prompted you to put up this post?

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#9
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Re: Pushing an Airplane: Free Energy (For Someone)

02/02/2008 8:04 AM

Yes of course I am kidding.

"What prompted you to put up this post?" There was a news item on national TV with footage yesterday evening of workers pushing the plane because the tow-bar was reported to be broken.

It was also reported that a new crowd took over the duties yesterday. (A newly awarded contract).

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#37
In reply to #5

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 2:48 AM

and flying all the way down to Australia. (Just dimantle the pane and throw it in the mail to have it back in Africa, the ultimate free energy experience)

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#67
In reply to #5

Re: Pushing an Airplane: Free Energy (For Someone)

02/12/2008 6:00 AM

Have you ever seen those guys jump. When I was in Kenya I saw them do thier traditional dancing and by gum those guys can spring up in the air. Maybe the collective force of them all jumping at the plane was enough.

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#68
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Re: Pushing an Airplane: Free Energy (For Someone)

02/13/2008 2:17 AM

It's pretty amazing. Check this out !

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#10

Re: Pushing an Airplane: Free Energy (For Someone)

02/02/2008 8:34 AM

The most amazing is not those 12 labourers to push it out to the northern parking, but there was another 12 labourers instructed by another boss to push it out to the southern parking. Both crews stayed working 12 hours before discovering the trick. They forced to held a meeting to solve the problem, the meeting continued for 12 hours, at the end the both crews agreed to exchange places with each others.

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#16
In reply to #10

Re: Pushing an Airplane: Free Energy (For Someone)

02/03/2008 12:37 AM

Wow - the news behind the news travels faster than the real news on the C2C (Cape to Cairo) route.

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#11

Re: Pushing an Airplane: Free Energy (For Someone)

02/02/2008 10:03 AM

Why dont they just park away from the terminal and have stair to the tarmac and buses to move passengars? Then the plane can do without all 12 laborers (a major manpower cost savings).


Btw, what the heck is a Gooz card?

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#17
In reply to #11

Re: Pushing an Airplane: Free Energy (For Someone)

02/03/2008 1:04 AM

The Airport is pressed with space already. 3 sides are clamped in by urban development. A quick glans at a map reveals a series of pans at the open side . (note this is my observation and may not be correct) As the area may be dolomitic it may not be safe enough for public purposes.

The Gooz card was derived from the "Get out of jail free" card from Monopoly. It is now called "Get out of Zim free"

You are now the proud owner of a Gooz card. -

If I can find my old game I might make one. I seem to remember words to the effect of "You may pass Go and collect $xxx"

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#22
In reply to #17

Re: Pushing an Airplane: Free Energy (For Someone)

02/03/2008 4:15 AM

You wrote:-

A quick glans at a map......

A Glans is the end of your Penis!, so you can read/see using this organ?

You should be in a Circus Sir, and make a lot of money!!!

glans

/glanz/

noun (pl. glandes /glandeez/) Anatomy the rounded part forming the end of the penis or clitoris.

— ORIGIN Latin, 'acorn'.

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#23
In reply to #22

Re: Pushing an Airplane: Free Energy (For Someone)

02/03/2008 4:25 AM

ROFLMPO !! Now we know why the 2 bird watchers got lost in the binocular challenge question !

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#24
In reply to #22

Re: Pushing an Airplane: Free Energy (For Someone)

02/03/2008 4:38 AM

Whole new meaning to:

"now look into my eyes, keep looking into my eyes. You will feel sleepy now."

I sometimes scare myself

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#25
In reply to #24

Re: Pushing an Airplane: Free Energy (For Someone)

02/03/2008 5:08 AM

....and when you read something wrongly, you can say "stupid prick!"

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#27
In reply to #22

Re: Pushing an Airplane: Free Energy (For Someone)

02/03/2008 6:14 AM

See with it, I think a lot of people think with it.

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#12

Re: Pushing an Airplane: Free Energy (For Someone)

02/02/2008 10:28 AM

Why did they not do what some planes (used to ?) do in Atlanta, Georgia, USA, they select reverse thrust and push themselves away from the terminal!!!

I was amazed the first time I saw it around 1987 or so.....

As to the laborers, I expect they used ropes. Height would not be a problem then....

Anything worth selling disappears fast in Africa......it gets legs and walks away!!!

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#13
In reply to #12

Re: Pushing an Airplane: Free Energy (For Someone)

02/02/2008 1:13 PM

I suppose the reason why they don't like doing the reverse thrust is for damage to the terminal building

It takes a lot of thrust pounds for the plane to move and perhaps the windows in the terminal cannot hold up against that. Somebody must know the breaking point of the windows?

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#18
In reply to #13

Re: Pushing an Airplane: Free Energy (For Someone)

02/03/2008 3:24 AM

Maybe there are no windows; but are people behind where the windows would be, if there were window which, unfortunately there are none--they got up and walked away before they could be installed.

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#21
In reply to #13

Re: Pushing an Airplane: Free Energy (For Someone)

02/03/2008 4:05 AM

I suspect you are right, or at least they were worried about what might happen.....or they never even considered the possibility, who knows?

Although just to move an aircraft on the flat cannot be that much power, plenty of very strong men have moved large aircraft for a bet, on their own!!

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#28
In reply to #13

Re: Pushing an Airplane: Free Energy (For Someone)

02/03/2008 9:48 AM

I believe that most of the bigger planes do not have reverse thrust. 737's do, 777's do not...

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#29
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Re: Pushing an Airplane: Free Energy (For Someone)

02/03/2008 12:58 PM

I personally cannot think of a large plane that definitely does not have it!! I have flown a lot and I do feel that I have experienced reverse thrust on most types, though I agree that it is not always used.....perhaps someone could tell us from the cockpit why?

I would have assumed that it was a CAA requirement for a modern passenger jet, what if the brakes failed? What if the runway is very slippery?

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#34
In reply to #29

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 2:00 AM

G'day Andy Germany.

  • perhaps someone could tell us from the cockpit why?

The preferred method for deceleration of jet airliners is thrust reverse as using the wheel brakes produces a considerable amount of wear and the braking mechanism has a limited life expectancy and cost a lot of money to replace.

As I intimated in my previous post jet airliners can stop only using wheel brakes but from take off speed you can only do it once as it destroys the brakes, tires and often wheels. On a 747 the test cost over US$1,000,000 to perform so it's normally only ever done once.

So, getting back to your question, with certain airports where there are curfews on when you can operate jet aircraft, due to noise abatement regulations, you can perform what is referred to as a tip toe approach during curfew hours.

A tip toe approach is normally carried out over water where there are no people to complain and has the engines throttled right back to the minimum thrust setting. The rate of descent is then controlled with the use of air brakes and the round out and flare or hold off performed as normal. Once the aircraft is on the ground full air brakes are deployed and when the speed has dropped sufficiently the wheel brakes are used to slow the aircraft to taxiing speed. The application of brakes is no where near what is used in the emergency stop during certification but it does increase the wear on the brakes. It also increases the distance required to stop and therefore requires a longer runway. Airlines are normally willing to accept the addition to the maintenance costs as it allows them to have the aircraft turned around and ready to depart the moment the curfew is lifted and that means having the aircraft in the air for as much as 90 minutes longer each day.

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#30
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Re: Pushing an Airplane: Free Energy (For Someone)

02/03/2008 1:13 PM

I think you'll find Andy's got a point, here.

What is true is that very few modern aircraft deploy reverse thrust during flight - tho' most use it after touch-down (particularly on shorter runways).

Some planes (generally military types) use it in flight to lose altitude rapidly in combat situations.

(Edit: damn! forgot to mark it OT, again. Sorry.)

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#31
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Re: Pushing an Airplane: Free Energy (For Someone)

02/03/2008 1:33 PM

...wasn't there an accident or two in the last 20 years or so when some engines deployed the reverse thrust cups while flying?

Thrust Reverser

This web link covers just about everything to do with reverse thrust, use of to back away, crashes etc etc...

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#32
In reply to #31

Re: Pushing an Airplane: Free Energy (For Someone)

02/03/2008 1:49 PM

I am sorry, I did not write that very well,

The only plane I know of that has enough reverse thrust capability to pull out from the jetway on its own power is the 737, and even they don't do it any more to save fuel.

There is some reverse thrust on most engines, ususally bypass on the turbo fans, that help slow down the air craft, but not enough to back it up from the terminal..

Even so the primary stopping force is the brakes..

However I am more than willing to be corrected if I am wrong!!

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#41
In reply to #32

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 5:49 AM

Steve, I disagree with your post in most areas and it would appear that you did not read the link I posted earlier at all, it describes that mostly all if not all modern passenger jet aircraft can use this to slow down. In fact they mention that it usually reduces the length of the landing roll to about 2/3rds of the normal! Quite some power in play here, if you are able to slow a fully loaded passenger plane down by 33% faster than without reverse thrust!!

Even some propeller aircraft use it to slow down by reversing the pitch of the props, I learnt that from the same link, it seems perfectly feasible to me!!.

If you also thought a little further in a logical manner in the way RT is applied, any reverse thrust so weak as to not be able to move an aircraft backwards, is also so weak, that it would also not slow the aircraft down either!!! This is also covered in the link I posted as being used to move backwards where a tractor push is not available....

Basically, you probably have 60% or more of the takeoff power available to the pilot(s) to being applied to stop the aircraft (depending upon throttle setting etc.), as all you are really doing is directing the thrust of the jets forward instead of backward!! The same jets as used to fly with!!

Other than some safety issues when slowed down of blowing rubbish up from the ground and it being sucked into the intakes, it seems a good method of stopping when the ground is icy or wet, so as to reduce the possibility of skidding!! The link covered all these points in a clear and simple way for most people I feel, may I recommend that you read it fully at some point? Here it is again:-

Reverse thrust

If you had ever been on an aircraft that used RT to stop/slow down on the runway (probably still cheaper than replacing expensive aircraft quality Brakes and tires I would imagine!!) as I have many, many times, you would know that when applied strongly, the braking effect is EXCEPTIONALLY strong indeed...and certainly no more stressful than taking off under full power, nor should it use any more fuel than taking off as generally RT is only used for up to 4 or 5 seconds or so......whereas takeoff and climbing to the point where noise abatement procedures need to be applied take far far longer.....

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#46
In reply to #41

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 7:39 AM

You're right Andy, I missed the earlier link.

From the Wiki link you posted here "The early deceleration reverse thrust provides can reduce landing roll by a third or more"

1/3 is not 2/3. And braking is applied at the same time as RT.. You have still not convinced me that there is sufficient RT available to pull a 757, 767, 777 away from the gate.

So I have admitted my original post was wrong, or at least badly written, and I will concede that I may still be wrong on the subject. But I am not convinced.

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#51
In reply to #46

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 9:01 AM

I wrote exactly as in the article, you appear not to have taken the time to read it more carefully and accurately. Taken from my previous post:-

In fact they mention that it usually reduces the length of the landing roll to about 2/3rds of the normal! Quite some power in play here, if you are able to slow a fully loaded passenger plane down by 33% faster than without reverse thrust!!

This means that they actually roll 1/3rd less, not 2/3rds as you misunderstood!!!!

It also takes an engineer to understand without needing to calculate other than in his head that if you can reduce the roll distance by 1/3rd of an aircraft when landing at speeds of around 160MPH with a full passenger and luggage load, that pushing back with reverse thrust at a walking pace is actually much much easier and requires far less energy for a very short time.......!! The article mentions this fact too if read carefully!!!

A 747 can weigh as much as 450 odd tons when starting!!!

The various crashes caused by RT accidentally being deployed in flight, sometimes leading to the disintegration of the aircraft IN THE AIR, almost always to a crash, (mentioned in the article as well!!) should also convince you that the powers available with RT are considerable!!!

By the way, I do not need to convince you of anything, only you can convince yourself or not once the facts are laid before you!!

Some people still believe in Fairies and elves/goblins etc.. they can have their fun too!!! Why should I try and spoil that fun by convincing them otherwise?

There are still people who believe in a flat world too......

I just lay the real facts before them......nothing more, believing or not is a personal thing.

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#54
In reply to #41

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 9:33 AM

"The early deceleration reverse thrust provides can reduce landing roll by a third or more."

From the paragraph on operation. I am some how missing the 2/3s Andy. Please enlighten me.

You keep insulting my engineering ability, but I am not detered. I am not convinced.

"With cascade reversers, net reverse thrust produced is typically 15-20% of the normal forward thrust (Rothstein, 2000). "

And at a terminal the engines will not likely be fully loaded ...

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#55
In reply to #54

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 9:54 AM

Ok Andy, I give:

I went and did the maths, and based on 15% thrust reversal, and assuming about 20% spool up and 4 engines going you get about 10,000 pounds thrust reversal based on a RR with a rated 58000 lbs thrust per engine. on a 747 with a take off weight of 875000 pounds assuming good wheels and thus a low coefficient of friction, it that should be enough.

It would be a noisy whirl wind on the tarmac though...

But I have been on plenty of 747's and I don't recall ever powering out... Maybe just me...

My apologies to all, I was wrong I admit I was wrong. You can stop beating me now!

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#44
In reply to #32

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 6:03 AM

Your are wrong on all counts. Thrusting back from airport gates is not that uncommon. Wheel brakes (as opposed to "engine braking") are never applied on landing until ground speed is reduced substantially by reverse thrust. Next time (all times) you fly in jet transport planes take note of the sounds (and feel) upon landing. First the engines seem to go silent (zero thrust) just before touch-down. A few seconds after touch down--when all wheels are down--the engines again "rev" up (as if trying to take off--if it's touch and go, the plane does take off); this is the engines actually increasing thrust, but towards the forward path of the plane--via the thrust reversers. After but several more seconds, the plane has slowed to the point where wheel braking (and nose gear steering) becomes possible and safe. Sometimes a plane can be reverse thrust and free-rolled to taxi mode with no application (at all) of it's wheel brakes until the terminal gate is reached. Occasionally, you will sense the transition from reverse thrust to taxi mode as a slight lurch forward in your seat as engines (the sticks) are backed off in reverse thrust mode. Someone mentioned reverse thrusting by military craft to lose altitude. The best way to lose altitude in a flight maneuver is to point the nose down and accelerate (increase forward thrust). The notion of reverse thrusting in flight for that purpose seems dubious from an aerodynamics and flight stability standpoint.

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#35
In reply to #31

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 2:14 AM

G'day Andy Germany.

  • ...wasn't there an accident or two in the last 20 years or so when some engines deployed the reverse thrust cups while flying?

There certainly was. In 1991 a Lauda Air (as in Niki Lauda the F1 world driving champion) B-767 had the thrust reverse mechanism suddenly deployed. The aircraft disintegrated in mid air due to the aerodynamic forces and all 223 on board were killed. You can read more about the incident by following this link to the Aviation Safety Digest Report.

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#33
In reply to #28

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 1:22 AM

G'day Steve S.

  • I believe that most of the bigger planes do not have reverse thrust. 737's do, 777's do not...

I don't know what your source for this little tit bit was but I wouldn't rely on it for much because it's bollocks.

Aircraft like DC-8, DC-9 (B-717), DC-10, MD-11, B-727, B-737, B-747, B-767, B-777 all have reverse thrust that is usually used during landing. However, they do have to demonstrate that they can stop an aircraft traveling at take off speed only using wheel breaks but this is normally only ever done once during the initial certificate of airworthiness tests as it destroys a set of brake pads and tires.

The only commercial jet airliner that I have seen that doesn't have and use reverse thrust is the Fokker F-28. The F-100 which was the replacement for the F-28 may also not have thrust reversers but I am not 100% certain and I haven't been on or near enough to confirm it one way or the other. However, on the photograph below I have drawn a circle around what looks suspiciously like thrust a reversing mechanism.

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#57
In reply to #33

Re: Pushing an Airplane: Free Energy (For Someone)

02/06/2008 9:08 PM

The only commercial jet airliner that I have seen that doesn't have and use reverse thrust is the Fokker F-28.

Right you are! The F28 and the F100 both had speed brakes (the tail opened up) (you can see the hinges just below the hinge gap for the rudder. The F100 had reverse thrust, but if I recall they had problems with it.

In fact, I just looked it up: http://www.casa.gov.au/airworth/airwd/ADfiles/over/f100/F100-050.pdf

I developed ground school training courses for the Fokkers -- nice planes, and a little more responsive to fly than many.

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#58
In reply to #57

Re: Pushing an Airplane: Free Energy (For Someone)

02/07/2008 9:28 AM

I worked and lived in PNG for a year or so back in 1983 and at the time the local airline Air New Guinea were operating F-28s on domestic routes around PNG and on the international route between Port Moresby and Cairns.

Garoka was an interesting place to land with parallel runways, one of arrivals and one for departures. Only hassle was that they ran in opposite directions as there was something like 1,000 between the altitude at the threshold and other end of runway, which by the way was lined with vary tall trees and a hotel. You would fly a level glide slope along the valley and the round out and hold of with a climbing attitude.

Bougainville was also somewhat weird as there was a mountain not that far off the end of the runway. If you tried to do a TVASIS approach you would hit the mountain before you reached the runway. What they did was install a second TVASIS approach system that was about 45° off the axis of the runway. The idea was that the co-pilot would fly the approach using the TVASIS not aligned with the runway while the pilot looked out to the left. When the pilot saw the TVASIS aligned with the runway he would take control and perform a 45° turn to the left. If everybody did everything correctly you would be ligned up with the runway and on glide slope.

You know I'm glad I don't work and live in PNG any more.

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#59
In reply to #58

Re: Pushing an Airplane: Free Energy (For Someone)

02/07/2008 11:25 AM

Gadzooks!

I use to live not far from a smallish airport (at about the lower limit of controlled airports) and the main runway was parallel to a large ridge. Invariably, some stressed-out pilot would get the instrument approach flipped over in his head, and fly right into the ridge on the procedure turn.

The F28's were sold to some very small airlines in some countries where there had never been prior local jet service. Standards in some of these places were a bit loose. One pilot, having just been made captain, was so excited that he took his passengers on a celebration sight-seeing flight through a fairly large city, at an altitude below the tops of some of the tallest buildings! He was captain for just one day, the airline not being quite that loosely run.

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#64
In reply to #59

Re: Pushing an Airplane: Free Energy (For Someone)

02/08/2008 1:41 AM

G'day Ken,

  • The F28's were sold to some very small airlines in some countries where there had never been prior local jet service. Standards in some of these places were a bit loose.

That pretty much sums up the Airline operations in PNG.

There was one commuter airline, lets face it everything airline wise in PNG is commuter, had a pilot on the books that crashed twice in one day.

At the time Air New Guinea operated 5 jet aircraft, 3 F28s and 2 very, very old and worn out B-707 aircraft. Apparently somebody ratted on them for operating the B-707s without carrying out the correct life extension programs and in one day they ended up with both of their long haul jets grounded in distant countries. The same week they had one of the F28s fall off the stands while undergoing undercarriage maintenance leaving them with only two operational jet aircraft.

A day or so later one of the F28s was trying to take off from Mount Hagen and aborted the take off twice due to insufficient power in one of the engines. He decided to give it a third try and about half way through the takeoff the engine went boom, separated from the aircraft and attempted to fly the remainder of the route without the aircraft.

Not bad, ending up with 80% of you jet aircraft US in a week.

It would have been laughable except on one occasion a flight from Port Moresby to Lae went missing after it diverted to Madang with my then girl friend and now wife on board. Phone calls to the airline resulted in them insisting the aircraft was in Lae which was total crap. Eventually I called a mate in air traffic control who went looking and found the aircraft on final approach for Port Moresby after leaving Madang. When I contacted the airline again to see if my girl friend was on board the said that the aircraft was still in Lae which was somewhat strange as it was now pulling up to the terminal in Port Moresby.

They also operated Islanders and on one flight on which I was a passenger into the highlands it got just a little close for comfort. Since they were only operating them with a single pilot I was sitting in the right seat and on our journey into cloud shrouded mountains the pilot managed to get lost. He eventually found a strip to land at and asked for directions to our destination. I decided that it probably wasn't a good idea to go tearing about in clouds that were more than likely full of rocks with a pilot that had already demonstrated his less than adequate navigation skills. The other three passengers elected to follow my lead and the pilot took off on his own insisting that it was perfectly safe.

It took over three weeks to locate the wreckage.

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#65
In reply to #64

Re: Pushing an Airplane: Free Energy (For Someone)

02/08/2008 8:05 PM

Poignant stories. They'd be funny, if they weren't so sad.

A friend taught flight attendants. One student was rehearsing lines for prepping passengers for a water ditching a mile or two short of the runway. The speech ended: "But don't worry, we have done this many times."

(She meant to suggest that they had practiced the drill many times.)

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#66
In reply to #65

Re: Pushing an Airplane: Free Energy (For Someone)

02/09/2008 7:06 AM

One of the aircraft used extensively in PNG was the Embraer EMB 110 Bandeirante. A top aeroplane but somewhat of a handful when operated with a single pilot as they did. Being a pilot if there was a chance I would always try and talk me way into the front right seat or flight deck. Unfortunately that's one of life's pleasures that is no longer available.

Anyway, I was sitting in the front right seat of a Bandeirante on a hop from Lae to Mt Hagen when the pilot leaned over and said the NDB at Mt Hagen was out so we would need to divert to Madang. Since I was in the cockpit I had a pretty good idea where we were and what we would need to fly over so I replied with

"Isn't Mount Wilhelm between us an Madang?"

The reply I received was pretty much what I was expecting and somewhat dreading

"Yes and we are going to have to go to 18,000 feet to make sure we clear it and there isn't enough oxygen on board for anybody but me."

I didn't completely loose consciousness like the rest of the passengers but boy, did I have a splitting headache that night.

The highest I have ever pushed it as a pilot without oxygen is 13,000 feet, but that was in a glider and I only used the height to set up my final glide so I was only above 10,000 feet for between 5 and 10 minutes.

Did you read about Steve Fossett and Einar Enevoldson altitude record of 50,699 feet. It was a bit of a cheat because they were wearing pressure suits but still not a bad effort.

Getting hold of equipment like this is not only exceedingly expensive but in Australia is completely impossible. We also don't have the sort of mountains they have in the Americas but there have been a few flights that have called it quits at about 30,00 feet due to the O2 running out.

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#39
In reply to #28

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 5:15 AM

I believe that if what you believe were true, a large percentage of commercial flights would be involved in fatal crashes every day. And, it brakes were used to slow those planes (that hadn't crashed) upon landing, most flights worldwide would be delayed by from hours to weeks...until replacement brakes were ordered, shipped, and installed. The plane and plane manufacturers would never be able to keep up; many airports would have to double their runway lengths; fares would be so high that the congestion problem would be solved for years and years to come.

Conclusion, all large transport planes (plane engines) have thrust reversers...or they don't take off. These are a major component...which adds greatly to engine price. And not only large planes...and not only jet planes....

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#40
In reply to #39

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 5:28 AM

There is no purpose or provision for actuation or deployment of (jet) engine thrust reversers in flight (where "in flight" is any time the plane is aloft during any phase of flight). In fact they cannot be, by design. If they are (due to malfunction or design flaw), it is an almost certain catastrophe. Plus, if a flight recorder indicated any plane flyer ever (so much as) tried to do this, or tried to defeat the mechanism that prevents this from being done (assuming such an attempt is possible), that pilot would be permanently grounded, for sure and for life.

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#45
In reply to #40

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 6:55 AM

You need to read the link that I have posted twice before you make such erroneous statements!

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#49
In reply to #45

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 8:06 AM

Since I am the one that started this mess, I went looking for answers…However I have yet to find a definative answer on reversing from a terminal other than it is generally not done due to noise and jet wash concerns. My personal experience (and I fly a lot) is that powered pushback is only done in small aircraft Fokkers, 737s etc. I recently sat for an hour in Amsterdam waiting for a tug to push us out on a 767.. But I am still willing to admit I am wrong, just not convinced yet!

From the attached paper http://swutc.tamu.edu/publications/technicalreports/167231-1.pdf :

There are two types of engine thrust reversers: cascade and clamshell reversers. Cascade

reversers are found on aircraft engines with large fans and high bypass ratios. When a cascade reverser is deployed, part of the engine nacelle slides backwards and a blocker door inside theengine deflects the airflow outward through a series of cascade vanes, which then direct the airflow forward. With a cascade reverser, only the airflow from the engine fan is reversed. The heated airflow from the turbine is still directed backwards. With cascade reversers, net reverse thrust produced is typically 15-20% of the normal forward thrust (Rothstein, 2000). Cascade reversers are commonly found on newer aircraft, including B737s, B757s, B767s, and all Airbus aircraft.

Clamshell reversers are found on primarily on older aircraft with smaller engines and

lower bypass ratios. Two large blocker doors are pivoted behind the engine which direct theentire engine flow forward. They are primarily found on MD-80s, DC-9s and older model B737s. With clamshell reverses, net reverse thrust produced is 30-40% of forward thrust

Pilots use a combination of reverse thrust and wheel brakes to decelerate during landing.

Reverse thrust is used after the nose gear of the airplane touches down until the aircraft slows to 40-50 knots, then wheel brakes are used to slow the airplane further. Engine manufacturers recommend using reverse thrust at speeds above 45 knots to prevent exhaust gas and debris ingestion (Rothstein, 2000). Reverse thrust is preferred by pilots on slick runways as a braking aid, when brakes are less effective.

The amount of reverse thrust used depends heavily on the runway condition, length, exit location, and exit configuration. On short runways, reverse thrust is used more intensely than on long runways. Because of the short runway, the pilot has little room for error and must slow the plane quickly. On modern runways with high speed turnoffs, the runway exits are angled, so the plane can exit the runway at a higher speed. On runways with right-angled exits, the aircraft has to slow almost to a stop before exiting. In both cases, the pilot may decelerate more or less heavily so he can take the most convenient exit.

Thrust reversers are occasionally used to back aircraft away from boarding bridges. This

is known as "power-backing". There are a lot of characteristics which determine whether or not an aircraft will be power-backed. These include location and type of engines, layout of terminal area, ample room, proximity of surrounding aircraft, and availability of ramp personnel and aircraft tows (Vance, 2000).

From the Herald Tribune on inflight deployment…

http://www.iht.com/articles/1991/08/17/thru.php

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#50
In reply to #45

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 8:35 AM

There is no error....other than what you by force of habit need there to be.

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#52
In reply to #50

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 9:10 AM

Then you DID NOT read the link fully......as some aircraft are designed for example, to use such control to allow them to make steep descents into a airport that may be surrounded by the enemy......

Quoting part of the article about reverse thrust in flight from Wikipedia:-

In-flight operation

Some aircraft are able to safely use reverse thrust in flight, though the majority of these are propeller-driven. In-flight use of reverse thrust has several advantages: It allows for rapid deceleration, enabling quick changes of speed; it also prevents the speed buildup normally associated with steep dives, allowing for rapid loss of altitude, which can be especially useful in hostile environments such as combat zones, and when making steep approaches to land.

Your statements were incomplete and therefore erroneous!!!

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#56
In reply to #52

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 10:21 PM

"Incomplete and therefore erroneous" is fallacious, especially as incomplete was by intention (as astute readers would have readily comprehended) in order to avert misunderstanding as to scope.... Nowhere was it said that reverse thrusting (including with props (pitch) as you pointed out...as did I also before that and before your link) was not done (with military planes--but unlikely with large transports), it was only said that diving was the faster way (implicit: the more likely way) to descend rapidly--whether larger or small plane (and within the structural tolerances). Thus the statement respecting the post you needed to nitpick about for sake of nitpicking is not inaccurate as, or in the way which, you characterized it. But I waste my keys since, as I said, it is your wont to seek disagreement as opposed to agreement. May I suggest that posting of counterpoints with the view to (non-belated) clarifications, in the spirit of seeking consensus or clarification of intent, as opposed to devaluing others for purpose of personal aggrandizement...would be better suited... (Do you now really thing I don't already know how you will respond to this?) I hope I am wrong, though.

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#14
In reply to #12

Re: Pushing an Airplane: Free Energy (For Someone)

02/02/2008 2:04 PM

Ah, but pushing with a rope is difficult. Maybe they also employed a bunch of magicians who know the secret ...

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#19
In reply to #14

Re: Pushing an Airplane: Free Energy (For Someone)

02/03/2008 3:26 AM

Not if the rope is between the legs going "backassward."

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#20
In reply to #19

Re: Pushing an Airplane: Free Energy (For Someone)

02/03/2008 3:32 AM

Or they lasso the empenage, hitch off the other end at the windsock and push on the bight in between 'til the plane's where it needs to be for taxi-ing or takeoff run.

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#26
In reply to #20

Re: Pushing an Airplane: Free Energy (For Someone)

02/03/2008 6:03 AM

Ok, I'll give you that - but as far as the rope's concerned, it's still more pulling than pushing (ie the rope is in tension).

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#47
In reply to #12

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 7:53 AM

Just a guess, but jet-thrusting back from gates might be done less these days to conserve fuel...my guess would be that it might simply be cheaper to pay the tractor and tractor operator to push the planes back. Noise issues and increased boarding gate congestion are other possibilities.

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#15

Re: Pushing an Airplane: Free Energy (For Someone)

02/02/2008 11:31 PM

Maybe a drive by or fly by passenger drop off with swinging gates to open like a scissors or wing of birds plane pulls up at 45 and pulls out in right sweep or left

BTh what kuzz point?

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#36

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 2:27 AM

My connection is not stable I Will do shorthand.

Gooz cards to all.

Reverse trust . . hmm.

Question:

Why don't they put rim motors on the wheels. The plain could revere by itself. and they could spin the wheels before touchdown.

I know I know! I have seen an starter motor that engaged at a speed.

and in Africa you will find the plane on bricks because the wheels was stolen.

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#42
In reply to #36

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 5:54 AM

Be an engineer, think about the wear and tear on the tires and the huge possibility of skidding if wet or icy. Also of a tire exploding if it wore too thin or got too hot of both together.

That should answer the question for you!!

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#38

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 3:00 AM

Ok, after the diverging, wandering, ducking and dodging, here's my assessment of the concept of pushing a 747.

To the best of my knowledge there is only one hard mounting point that can take the force required to push back a 747 or any large aircraft for that matter and that is the nose undercarriage. It's all to do with the force and aft loading of the system. The main undercarriage is primarily designed to absorb and tolerate vertical loads, however, it designed to take a fair old sideways load as during a cross wind landing the aircraft will not be traveling with respect to the ground along its longitudinal access. Cross wind landing techniques are designed to minimize this side way loading but there will always be a certain amount of sideways loading at the moment of touchdown.

The other major force the main undercarriage needs to cope with is the longitudinal rearward shearing force associated with touchdown and braking with wheel brakes. The main undercarriage while not specifically being designed as a hard mount for ground handling it can withstand a hefty reward force that is certainly well in excess of the force any group of humans could apply.

Ok, So far we have established that by pushing on any and all of the undercarriage legs you could more than likely supply enough force to move the aircraft backwards without damaging the aircraft. So, how much force does it require and how do we do it?

The force required will vary dramatically depending on how long the aircraft has remained stationary and how long since it last landed. The pressure within and shape of the tires will change over time and aircraft that have been left to stand overnight will develop somewhat of a flat spot . This isn't enough to effect the operation of the aircraft but it will often cause a considerable amount of vibration during the first take off of the day and pilots will often warn passengers of this prior to takeoff. The pressure will also drop after a landing due to the cooling of the tire and nitrogen used to inflate it. The lower the pressure in a tire the greater the distortion and the harder it will be to push. Anyway, the force required to get a 747 moving is fairly great but I have read of an incident where for a bet somebody tried to successfully move a 747 using a large piece of wood wedged under the nose wheel. I haven't aver been able to confirm this but it doesn't sound that off the planet so it may be true. If it is then having a host of really strong dudes push an aircraft wouldn't be completely out of the question.

Now to the how, the easiest way to push a vehicle that is on wheels that are completely exposed is to push the top of the wheel in the opposite direction that you want the object to move. If you got 18 big strong people, one on each wheel, all pushing the to pf the wheels towards the from of the aircraft there is a fairly good chance you would be able to get the aircraft moving backwards all be it at a very slow speed.

Mind you, I wouldn't fly an aircraft that had been manhandled like this without having a very detailed and extensive series of inspections as well as somebody that really knows what they are talking about supervising. There are lots of fairly delicate and easily broken components on the under side of an aircraft that could easily be damaged. Sixteen big muscle brained below average intelligence mugs and trying to do something as idiotic as push some 400 plus tonnes of B-747 by hand is about as good a recipe for disaster as you can get.

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#43
In reply to #38

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 5:54 AM

Hi Masu - It may not have been a 747. I was in the next room during the news flash and only caught the last few frames.

According to the news flash - the push-bar normally used to connect between the nose gear and tractor were broken. and they had to push the plain back by hand. I don't think is was the only plane that were pushed.

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#53
In reply to #43

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 9:33 AM

I'm not quiet sure how the 747 slipped in but none the less everything still applies.

Ground handling of aircraft is considerably more difficult and prone to damage than most people realize. It's often called hangar rash and it's not uncommon to find some dint, scratch or scrape that has been caused during ground handling.

The thing that makes aircraft so prone to damage is that the in flight conditions they are designed around don't normally produce point loading but rather distributed loads. That makes them really easy to damage by pushing anywhere that hasn't specifically been designed and reinforced to cope with a point load.

In response to the guests post #41

  • There is no purpose or provision for actuation or deployment of (jet) engine thrust reversers in flight (where "in flight" is any time the plane is aloft during any phase of flight). In fact they cannot be, by design. If they are (due to malfunction or design flaw), it is an almost certain catastrophe.

I have never seen it documented and have definitely not tried it myself, but in the event of a deep stall and fully developed spin it is very easy to go past VNE (velocity never to be exceeded) while trying to recover normal flight. If you attempt any sort of control input while traveling faster than VNE you will overstress the airframe and probably rip the control surface off the aeroplane. One of the techniques I have heard anecdotally is to reduce the airspeed the use of reverse thrust on the inner engines may be preferable to attempting to maneuver at speeds above VNE.

So far we have only discussed the use of reverse thrust on aircraft that use jets or fan jet engines but some propeller driven aircraft that are equipped with constant speed or variable propellers can also utilized reverse thrust. It is don by varying the pitch of the propeller so that the thrust it produces is reversed.

The C-130 Hercules is one such aircraft and the reverse thrust it produces can dramatically reduce the landing role.

PS I just realized that in my earlier post I had inadvertently stated that you need to push the top of the wheels in the opposite direction to which you what the aircraft to move. In reality you need to push the top of the wheel in the same direction that you wish to move the aircraft. By pushing the top of the wheel you have effectively double the force you are applying to the aircraft.

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#60
In reply to #53

Re: Pushing an Airplane: Free Energy (For Someone)

02/07/2008 3:22 PM

In response to the guests post #41 Masu's well-phrased and well intended counterpoints (the same with which no disagreement is intended), the following edit/rewrite with clarification, of post #41, is offered:

  • >Keeping with the seeming context of Hendrik's OP, and some other posts (including with the seeming context and comprehension...in the post to which #41 was specifically meant to reply), my information is that< Tthere is no >(possibly, no approved)< purpose or provision for actuation or (apart from pre-touch-down deployment) >for power-up< of (jet) engine thrust reversersreverse thrust, in flight (where "in flight" is any timewhen the plane is aloft during any landing-approach phase). In fact >—this base on representations by civilian commercial passenger transport pilots—< they cannot be, by design. If they are (presumably, due to malfunction or design flawoverride), such is >has the potential to to be< an almost certain catastrophe >, if not to the craft then possibly to unrestrained cabin crew members or passengers (caught unawares)<. >Bear in mind that this assertion might not, and probably does not, apply in the cases of: (1) military transport planes (large transports in particular...being also what Kendrick's OP, and numerous succeeding threads, seemed to be alluding to) and similarly-rated planes used in other services (smuggling, even), which by design are intended for the possibility of more stringent—even extreme—flight regimes and conditions; and (2) in the case of variable-pitch-prop-propelled planes (such as the Herc that was just mentioned—albeit that variable pitch used in reverse-pitch was mentioned in passing previously by no less than your's truly).<
  • >In the case of passenger transports, it was those pilots mentioned above who spoke (to this writer) of interlocks (or something to that effect) incorporated, apparently as fail-safe's, in the engine and flight control systems (manifested at stick/collar assembly) which prevent the inadvertent application of reverse thrust in passenger planes during powered (cruising) airborne flight.<
  • >Given the fatality incident stemming from such inadvertent use which was mentioned earlier on this board, and the stringent flight dynamics (wing bank/descent rate/etc.) limitations imposed on passenger plane operation, it stands to reason both, that thrust reversers be mandatorially installed and that inadvertent thrust-reverse fail-safes are incorporated, as a condition of FCC airworthiness certification (of "applicable" commercial passenger planes)<.
  • >As to prop-driven commercial passenger transports (but not speaking with authority in this wise), it seems reasonable to surmise that, as with jet planes, reverse pitching of propeller blades finds most typical, if not (practically) exclusive, use during landing operations, after touch down (after engine throttle-down prior to "reverse power up").<

To all with whom my (pre-edited) post#41 has inadvertently drawn us into disputation, mea culpa is offered...in that discussions on boards present pitfalls which are all too easy for participants (this writer not being immune) to fall into:

  • When a discussion is, or seems to be, expanded beyond the original scope...
  • When, as seems was the case in post #41, in the interest of brevity, insufficient context information is provided or reiterated...
  • When it is not known (and consequently assumed) to what degree readers will both perceive the context, and be able to read-in context and meaning that is not specifically (or comprehensively) spelled out...

For these and similar omissions, and for items misstated in haste, post number 41 author apologizes to any to whom apology is due...and appreciates the reminders concerning the need for more care and circumspection in the making of posts--especially to discussions in which "topic context creep" has or might have occurred.

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#61
In reply to #38

Re: Pushing an Airplane: Free Energy (For Someone)

02/07/2008 5:08 PM

Now to the how, the easiest way to push a vehicle that is on wheels that are completely exposed is to push the top of the wheel in the opposite direction that you want the object to move.

My goodness, you've gone daft. Have you never rolled a wheel after changing a tire, or rolled a hoop with a stick, or rolled an open wheel car? You push the top of the wheel in the direction you want the vehicle to move.

BTW, the max takeoff weight of a 747 is 750,000 lb or so, and the coefficient of rolling resistance of the tires is about .013 (or higher when flat-spotted) so about 9750lb of force would be required. Tough job for 18 people (541 lb per person) even if burley. Hard to exert enough force, but doubly hard to get enough purchase while maintaining foot traction.

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#62
In reply to #61

Re: Pushing an Airplane: Free Energy (For Someone)

02/07/2008 5:39 PM

(Ken - see Masu's #54)

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#63
In reply to #62

Re: Pushing an Airplane: Free Energy (For Someone)

02/07/2008 6:34 PM

Thanks -- he hasn't gone daft after all! I sometimes jump around in these threads reading only some of the posts. My Bad.

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#71
In reply to #38

Re: Pushing an Airplane: Free Energy (For Someone)

02/14/2008 9:39 AM

"is to push the top of the wheel in the opposite direction"

When I first read "top of the wheel" I thought of mechanical advantage. But opposite direction? Is there some advantage to rocking backwards, or what?

Fyz

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#72
In reply to #71

Re: Pushing an Airplane: Free Energy (For Someone)

02/14/2008 10:22 AM

(Fyz - see Masu's #54)

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#73
In reply to #72

Re: Pushing an Airplane: Free Energy (For Someone)

02/14/2008 10:51 AM

Thanks

Fyz

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#48

Re: Pushing an Airplane: Free Energy (For Someone)

02/04/2008 7:56 AM

Those of you who are giving yourself good answer votes, some one is probably taking names and making a list.

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#69

Re: Pushing an Airplane: Free Energy (For Someone)

02/13/2008 5:52 PM

If you can do it with twelve otherwise unemployed men, why not?

However, there is a precedent. During WW-2, the Luftwaffe had the Me 262 jet fighter, but fuel was scarce, and they hated to waste fuel by taxiing to the end of the runway. They used oxen to tow them. Surely, there are oxen in Africa.

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#70
In reply to #69

Re: Pushing an Airplane: Free Energy (For Someone)

02/14/2008 1:28 AM
  • If you can do it with twelve otherwise unemployed men, why not?

Because there's a very good chance that the 12 unemployed people wouldn't know what they are doing and cause serious and possibly even catastrophic damage to the airframe.

Aeroplanes are designed for distributed loads and don't take kindly to being pushed, pulled and prodded in places not designed for it. For example if you push on the wingtip it's not difficult to overstress the wing spar and substantially reduce its strength. Wingtips are often made of very soft material that easily deforms with highly visible signs of damage. This not only protects the spar by limiting the force that can be applied but give a very visual indication that something has gone terribly wrong and there may be hidden damage.

Then you have the danger of working around aircraft on the apron. There are a host of ways you can get injured or even killed if you don't know exactly what you are doing. For example the noise created by a jet engine can cause permanent damage to your hearing in less than 10 seconds if you are not wearing the correct hearing protection. Communications are also a problem as are propellers, jet exhausts and intakes. You can be throw a considerable distance by a jet wash and a spinning propeller is all but invisible.

Finally you have the security side. Would you want some totally unvetted person having access to the aircraft you are going to fly in?

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