You said it.

Why they still use pitot tubes, when latest GPS systems are available.

May be some body sitting inside the plane, with hand held GPS, might be measuring the speed (just as time pass) more accurately than the autopilot /pilot measurements!

Gsuhas,

GPS does not provide airspeed and Groundspeed would not be very useful to a plane in a storm or a fast headwind or tailwind.

There is a tight margin between stall and sound barrier. They call it that margin "coffin corner" for a good reason. Stall and you fall, overspeed and you hit the sound barrier and your plane can easily break apart.

With a false low speed indication and a hand on the throttle what do you think you would do?

Jon

kkdwlr

Come on! You may be expert of aviation, which I am not.

But simple matematic tell me that with mean earth radius of 6370 kms and normal flight height of 10 kms from ground, the ground speed will be about 0.15% less than air speed. This percentage will be almost same at polar radius as well as at equatorial radius of the earth.

Thus, with air speed of 800 kms/hr, the indicated ground speed by GPS may be 798.75 kms/hr.

Will this difference really matter and will cause wrong indication to stall the plane to fall or rip it off by high speed?!!!

Is the speed window so narrow?

Getting back to previous, all aviation for better or worse runs on sensed airspeed and altitude.

The most important point not being to be absolutely correct (which GPS is most certainly not either) but to be generally wrong in a group.

So at approximately 18,000 feet all aircraft turn the barometric correction factor to 29.92 (which is bound to be wrong) so they are all uniformly wrong.

So aircraft separation will still work.

This is not certainly the answer to my point and mathematics I gave in favour of using GPS and about the ground speed and air speed difference being measured by GPS.

Yes, at that altitude, the window of safe speeds is pretty narrow. And your math is not taking into account winds aloft which can be pretty dang brisk at that altitude.

Did I mention headwinds? GPS doesn't do airspeed.

Trying to compensate for erroneously low mach speed in a storm is deadly as your plane is already buffeted and the sound barrier broken by going from accelerating from a tail wind and hitting a 200 hundred mph storm headwind.

Low airspeed and variable headwinds can get you into a stall situation. The radical corrective manoever scares the hell out of passengers.

Airspeed versus ground speed is not a simple mathematical calculation.

A plane can be going down the runway at 100 mph into a 50 mph headwind. that would mean a groundspeed of 100 and airspeed of 150 mph.

I was in a plane that was approaching an airport in a headwind. We got above the apron and landed vertically on the apron instead of the runway because of the speed of the headwind. Our ground speed was zero and GPS would not have known the speed of the wind.

Vertical takeoff was interesting too.

Then we overflew the sea ice airstrip and circled across the Soviet border and back to make sure if we could land safely at Diomede Island to dump cargo.

That's one of the things they don't mention about the postman getting the mail through.

And the A330 is not made like a 1948 Buick.

Jon

Air speed can be different to ground speed by several hundred miles per hour.....think of the jet stream as a good example.....

I am not only refering to your post.

I am unable to understand what is "Air Speed". I am assuming that what Air Speed we are refering is speed of the plane in the air (Distance /time)

But from the various posts I am confused. Are we refering Air speed as speed of air with respect to air?

If what I am assuming is correct, air speed of the plane should be irrespective of speed of the air and its direction.

Airspeed is the speed of air passing over the airfoil. If you are parked on the runway and have zero ground speed and are facing a 40 knot headwind, you are starting off with a 40 knot airspeed before the wheels even start turning. if it is a 40 knot tailwind you have a NEGATIVE airspeed of 40 knots.

Since lift is a function of the movement of air over the airfoil, you can in fact have a zero or even negative ground speed and still have enough airflow over your wings to keep you aloft if the wind is strong enough.

All this is possible before you even start your takeoff roll.

This is about as basic as it gets with respect to aviation.

Now imagine you are flying in a violent thunderstorm and the wind is changing direction and speed by tens of miles an hour by the second. No human can play with the rudder and the throttles fast enough to keep the airspeed even CLOSE to stable under such circumstances. The computer must maintain the airspeed by constantly adjusting the throttles. It senses the airspeed using the Pitot tubes. but if two or more of the tubes freeze up, then the computer has no verified airspeed data to work with.

Since they found the Vertical Stabilizer virtually intact and floating, and the aircraft did apparently make a radical bank right before going in. I have to wonder if this is another case of the Vertical Stabilizer coming off in midair due to turbulence. This has happened before in NYC if memory serves on a similar aircraft (A-300). It was put down to flying through strong wingtip vorticies causing a structural failure. Some people believe that aggressive use of the Rudder Pedal can cause structural failure.

I'd be willing to bet the pilot was really leaning on that rudder petal that night. I'd be willing to bet the plane was experiencing severe lateral g-loading as well.

Great. Thanks. GA

I learnt much more than what I was knowing few minutes back

This website indicates that the A330 and the A300 which it replaced have a very similar, if not virtually identical (at least structurally speaking) vertical stabilizer, and the aircraft was designed prior to the 2002 crash of American 587 (it was built in 2005, so there may have been some structural changes between 2002 and 2005, but Airbus never admitted it was a structural deficiency, they insist that it was due to pilot error. I suspect that AA587 may get reclassified as a structural problem after this investigation shows another broken off tail.). Therefore it would have similar mounting structures. The avionics was updated with software limits to prevent the pilot (or autopilot) from making large rudder movements at high speed, but that will of course assume that the flight control computer knows just how fast the aircraft is flying, which if there was a problem of the pitot tubes icing at high altitude, it is quite possible it did not receive accurate information. This might have set off a whole series of events that eventually caused the tail to shear off and the pilot lose control of the aircraft. That also assumes it wasn't a sudden wind shear that caused the failure and not rudder movements.

The electrical problem that the telemetry noted might have been due to the aircraft breaking up bit by bit while the pilots fought for control of the aircraft. A symptom, not a cause.

See message 122.

see post # 85 ..

this aircraft may have been on the schedule for pitot tube r & r. it wasn't an eco , or fcd. it was routine maint, scheduled maint. maybe even a time control change item, don't know their maint schedule.

I read where Air France started changing to the better Pitots even before Aerospatial had confirmed their research.

Some airlines like to keep pace with the OEMs improvements and some go with the idea that if it doesn't exibit a problem leave it alone and rely on routine inspections per maint schedule.

Wrong.

If for example you have say a 200mph head wind and you are flying a small aircraft with a top speed of 200mph. You will be staying still (but still flying in the air) = ground speed 0mph and airspeed 200mph.

Airspeed is what keeps a plane in the air, ground speed has little relationship to this.....Do not confuse the two.....

Which is why airspeed is the more important of the two for an aircraft.

By the way, Air France has started changing out the damaged Pitot tubes that they were told to replace in September 2008!!!

Starts to sound like what happened to Concorde, Air France deciding what NOT to install, in spite of the fact that the manufacturer recommends it.....perhaps they have killed a load more people.......

I do not travel on French Ferries because they are often in such awfully condition, as it would appear are some Air France aircraft...... Lucky for me, I can decide which lines to use or not!!!

Yes Andy, I understood my mistake. Thanks for it.

Regards

We all have our individual blind spots, I include myself fully in that area, you have just "joined the Bunch" so to say......no big deal, just welcome.

Have a great day!

I tend to think that Air France is up to par with the bells and whistles on their fleet.

I don't expect planes to survive every situation they encounter. Especially errors by the crew.

Jon

Well if they are just now getting around to refitting the aircraft with Pitot tubes that don't ice over, then I'd suggest that they probably have been slow to implement other upgrades as well.

There is nothing like having all the horses wander off to get you to thinking about closing the barn door.

If you read about what Air France DIDN'T do to their Concorde fleet, which contributed immensely to the "ONE AND ONLY" Concorde crash (The British Airways Concorde fleet had special "Guards" to stop both water and rubbish from the ground being thrown up at the wings/engines), you would not be so happy with Air France's qualities....or record.

The Concorde crash "reasons" had already occurred with a (BA) Concorde taking off from the USA (debris on the runway) sometime before, the only difference was that the escaping fuel did not catch fire......the makers did some clever redesign work to disallow it happening again, but Air France were too clever and decided to save money.....which reminds me of an old German saying "They saved money, no matter what it costs!"

If all aircraft types were stopped flying after just one crash, Boeing for example would only have one flying type, the 777 I feel (Haven't seen one of them crash yet I believe). The 747's would be long gone!!! As would every other Boeing type....

BA had actually not lost money on Concode for some years and it was good advertising and a "show the flag"....BA even made further expensive changes to all the airceraft, but the licenses were still revoked.......I wonder if there was some strong (non European) political efforts made to get rid of them, behind the scenes?

in 86, the Concorde came to Oakland . i forget when it was in SFO.. but i do remember the take off... pattern clear , no take offs for , iirc , 15 minutes after Concorde departed.

if you ever get to sfo, in the central terminal, is the noise abatement display.. glassed in room so everybody can see , a very nice map of the sfo area, complete with all the noise sensors and the readings, in real time.. you can watch the take offs progress and the sensors light up with their readings..

from the public the major complaint at the time was the noise level from that airplane at takeoff.

the vortices from that may have lasted a long time as well, with the " hub & spoke " approach to air traffic mgt by the airlines...that extra 10 ~ 20 minutes would snafu the connections .

although that maybe a very short sighted approach,.. goes fast makes tooo much noise..wake turbulence is toooo much ...

imho: i think that's the main reasons..

also why the SST hasn't been developed further...

few us airports have the vision to do what SEATAC has done...( sry .. haven't figured out how to make bold or underline , yet )

Obviously you were never around when a 707 was taking off years ago......I flew on 707s many times, they were only subsonic and just as loud as Concorde it would appear!!! Probably banned today on noise signature......as well as fuel usage.

You appear to be judging Concorde against modern aircraft which is sad and unfair, it was designed in the 60's....first flew in October 69.......judge it against other aircraft of the time.....

Compare more carefully........remember, except for one preventable crash, a completely unblemished record........try for instance putting $10,000 on a plane type today and bet that it only has a max of one accident in 30 years of usage..........you will have great trouble in finding one.....I personally would not bet at all......and remember, Concorde was the ONLY one of its type, even today......

Forget mentioning Concordski, it was an unmitigated disaster, even though it was supposed to be a copy......!! The fuel system was useless and caused a lot of its problems.

Concorde's fuel system was a full military type with sophisticated fuel movement s<ystems to "fly/balance" the aircraft better....

By the way, the turbulence of the larger aircraft around today is even greater....its a problem the aircraft industry must live with......CAT detectors for example.....

with all due respect:

i wasn't judging the airplane at all.. in fact i was surprised at how narrow the crew passage was. and the banks of c/b's. and the crew dipped the nose for , as i stood there with my camera, very nice of them. and on the preflight walk around i marveled at the landing gear.

i might go so far as to say , Jet Blue took the interior scheme and put that into their business plan.

my point about Seattle: the airport bought up the land on the route of the approach.

as to Stage 1 a/c vs Concorde , or Stage 3 requirements..

my other point is : the popular notion that pax's want their cake & eat it too..

don't like the sound, but want the speed.. is and shall always be unrealistic and very short sighted.

my other point : was to your notion about forces other than European politics behind the grounding of the aircraft.

hope this clarified my previous post.

You wrote:-

hope this clarified my previous post.

I can say somewhat only......

Concorde was for an Elite group of well monied people, I only went on it once (by invitation) to have lunch in Egypt and back to the UK....kind rich Brother in Law......I had completely forgotten about that trip till today, strange how the mind sometimes (doesn't!) work!!....

I was always planning on a round trip to the USA with my wife for a "short weekend" holiday. Sadly, never got around to it.....

I have been passenger in a few RN jets (Jolly only) over the years (60s to 70s), but Concorde was something else.....refined.....

(the deck landings on a carrier tend to loosen the sphincter/bladder a bit for the untrained, at least the first few times, fly empty was my motto!! I was only along as 2 legged ballast)

Progress......

sorry if you didn't understand me.. i looked at both my posts .

i can't imagine how you construe that as an attack on the plane..

The land at the ends of the SeaTac runway are parks or industrial facilities.

A friend has a place just east of the approach from the North. The tall trees don't get taller because turbulence rips of the top leaves and limbs.

After approaching airplanes go over you can hear the air loudly ripping from the turbulence.

Now there is a third runway. Prior to the third runway people on west side got excited and were selling their property at a loss. That same friend's brother bought a nice place for an unbelievable price. With the quieting of the engines it is not a bother.

Before the Russians got quieter engines it was a problem when they took off to the north.

I lived 7 miles north in the city and sometimes the Russians flew too low on the approach and we thought they were trying to clip our chimneys. They got a lot of grief over that.

Jon

chances are good that that article i read was from a few years ago, it was about how the noise abatement was being handled..how Seattle's growth was compared to SFO growth in the 50's. & i hadn't done any research currently to verify that was still the practice, it was my assumption.

iirc: the article was comparing the way different communities were approaching the need to have an airport and the need for housing.

and especially when the housing moves into the close area around an airport that is already established , then the " new " house owners complain over the noise.

thankz for setting me straight.

It seems that some folks don't mind the noise now that it is abated and going green has put a lot of noise dampening insulation in houses.

Of course a lot of aviation related people probably live around there and don't mind.

The friends I spoke of lived in my neighboorhood under the flight path in Seattle before moving just north of the airport.

Long before we lived in Seattle (1951) a B50 crashed on an apartment not far from our neighborhood.

New planes doing their first flight from Boeing at Renton to Boeing Plant 2 / King County Airport in Seattle go over my house. A lot of other aircraft make their runs over my head too.

We have a few Volcanoes in the area and big earthquakes to consider too. So what's a drive on the Interstate or a plane ride through some turbulance to us?

In Houston the FAA is about to force a whole bunch of landowners in the sound corridors of IAH's runways to accept limitations as to what they can do with their property after the fact (we do not have zoning here nor do we want it. we feel like you own your land and not the government and you can do whatever you want to with it within the limitations of your deed restrictions which govern land use.). It is not going to be a pretty fight. It is essentially an illegal taking, but given the stupidity of the Kelo ruling it will probably stand.

I am losing track of what even is known.

What I know is that any pilot knows that if they fly any aircraft into a thundercloud, they are taking a risk.

I believe the primary cause of failure is loss of the vertical stabilizer similar to FL587 that crashed into Brighton Beach in 2001. FL587 was on takeoff and as such did not survive long enough to have spurious messages. FL 447 at 10,000+ m would have survived long enough to send trouble messages. As the APU is in the tail section, and various flight controls and electrical buss components pass through that area, it's very possible that loss of the vertical stabilizer caused the loss of electical components, followed shortly thereafter by loss of the aircraft.

Yesterday on a news thing I saw what looked like the tail section with the distinctive Air France tail logo floating in the sea.

Hi,

back to lightnings:

if an uprising cloud separates charge the positive charge is accumulated in the upper part and the negative charge in the lower part of the clouds.

Most lightnings exist between differently charged lower clouds, some between lower clouds and ground, few between upper clouds and lower clouds and very very few between upper clouds and ground.

Often some surrounding winds carry the upper clouds and the accompanying charge over considerable distance so that severe lightnings can hit miles away from the thunderstorm.

A lightning will discharge a volume of charged air-moisture-droplets-icecrystals - the higher the volume the higher the charge.

Lightnings from upper clouds carry much more charge and energy and hit typically with megavolts and near mega-amperes.

Aluminum tubing 100mm (4 inch) diameter and 6mm (0.25") wall-thickness will melt down if hit by such a lightning. This is 6 square centimeter or near 1 square inch. (These data are from a medium size thunderstorm with maximum clouds at 12 km only)

How much of the aircraft skin would be molten or at a temperature of immediate failure at such an unlikely - very big hit?

Other possibility: for how long will the pilots be blinded if a lightning is passing by very near the cockpit windows? This in parallel with an impaired flight control system?

RHABE

Earlier entries have gone into detail on the Lightning issue. Take a look.

MegaVolts and near mega-amperes occurs for such a short time that little power can be attributed to it.

Lightning hitting a large surface area does little to the metal or even the paint.

It isn't like a focused energy burst from a Romulan warship.

Aircraft and thier electronics are designed to handle the zaps from lightning.

Hi,

this is true only for the low energy lightnings that can be handled by around 1 square centimeter of copper or aluminum.

But the big ones from the positive charge cloud up between 8 and 17 Km will melt easily one square inch of aluminum.

As this happens in a very short time this melting is regardless of shape (if bar or sheet) so at 1/20 inch sheet thickness a 20 inch region of any length would melt within microseconds to milliseconds. As only half the melting temperature is needed to reach complete loss of strength there may be complete failure by one of these hits.

Once more: this is very unlikely but it happens.

RHABE

"big ones from the positive charge cloud"?

"From the positive charge cloud" is not an accurate term when talking about lightning. The sparks don't come from a positively charged cloud or anything else.

If lightning struck a small point its energy can do some damage to the small point.

If it strikes a large metal surface it would not strike it in a concentrated manner.

As was stated previously, a lightning strike is so rapid that it causes skin affect and passes on to the other less charged "cloud" that the plane got between.

Compare the high voltage discharge between 2 needle points and the discharge between 2 large smooth surfaces. The distance for discharge between sharp points is considerably shorter than the distance for discharge between large flat surfaces.

On the ground, the energy of a lightning strike would be more energetic so lightning arresters (sharp points) are used to keep those bad boys away from the big smooth bodies of aircraft and people around them.

Hi Kudukdweller,

you mix up something:

"If it strikes a large metal surface it would not strike it in a concentrated manner."

Why not? The "Fulgurites" found in sandy areas are remains of sintered quartz sand and have typically diameters of 30mm or 1.2".

The high current density and the related magnetic field is resulting in a "pinch" of the current path, the magnetic forces tend to concentrate the region that is current conducting and the pressure is acting against, so with some hundred kilo-amperes only a current cross section of 1 sqi or 6cm² will result.

"a lightning strike is so rapid that it causes skin affect"

This is true only for the first 10 to 100 µs and during this period a large voltage drop develops along the path and this is triggering secondary paths through the structure and the inside.

You are right with the breakdown voltage between sharp needles compared to flat electrodes. But if long distances are to be bridged by the lightning everything changes a bit. The sharp corners still attract the lightning by a high field strength. But midair the lightning has to form "streamers" of pre-ionised air with an invisible very feeble first try and then use these conducting pathways to discharge its energy. Because limited voltage these streamers do have only a length of some 100m and this causes the lightnings deviation from being straight: at the end of the first streamer the next one starts with a slightly different direction.

"From the positive charge cloud" is not an accurate term when talking about lightning."

The upper layer in any thunderstorm is positively charged (with respect to earth ground potential) and the lower layer is negatively charged.

Why not call the upper layer the "positive cloud"? Lightnings from there are extremely rare and extremely powerful!

RHABE

"The "Fulgurites" found in sandy areas are remains of sintered quartz sand and have typically diameters of 30mm or 1.2"." They are formed when lightning with a temperature of at least 1,800 degrees Celsius instantaneously melts silica on a conductive surface and fuses grains together.

The sand was not up at 39,000 feet on an aircraft.

A sand strike offers a unigue power dynamic to lightning that is quite different than a big flying metal tube that is just a pathway for a big spark.

"high current density and the related magnetic field"

What effect does the lightning generated magnetic field have on the lightning? Is it the same as applying a short-lived high current spike to a conductor?

"The upper layer in any thunderstorm is positively charged (with respect to earth ground potential) and the lower layer is negatively charged." "Why not call the upper layer the "positive cloud"? Lightnings from there are extremely rare and extremely powerful!"

Your charge theory seems clouded. How would you know what charge is in a "layer"? Why would you think lightning would have to jump from a positive charged cloud or layer to a negative charged cloud or layer. How would you test your theory?

Why would you think upper layers have to be positive and lower layers negative? If they are, what direction would the spark jump?

If an aircraft is hit by lightning while passing between two side-by-side unequally charged clouds that are trying to equalize, what direction would the spark travel?

http://www.nap.edu/openbook.php?record_id=898&page=90

The Earth's Electrical Environment

Hi Kudukdweller,

I agree that sand (dry or wet?) may give rise to an abrupt change in the current path of a lightning - I don't know if or if not.

Any current in a conductor will compress the conductor. In solid ones only low stress is the consequence. No 100K- to 1M- amperes will be possible in solid tubes to see the compression. (Only in the z-machine, have a look to the Sandia National Lab webspace). But in a compressible plasma channel any current will compress the channel.

Look in a physics book about forces between two parallel currents in conductors.

"flying metal tube that is just a pathway for a big spark"

How much current for how much time will be needed to lower the strength to failure?

1 square inch aluminum is not a small cross section to convert to a melt.

"Your charge theory seems clouded." That's not my theory, look at the book at the link above.

"If they are, what direction would the spark jump?"

The spark originate with streamers (fast and not visible to us) from the negative side, electrons that are pulled by the field, these ionise the streamers until near the other side, then the positive side too will generate streamers, if the two sides unite then the first main strike occurs, followed immediately by a counter-streaming second one and may be some more back and forth.

So most sparks travel in both directions, the first start is from the negative side, electron movement is dominant.

Look at the separate chapter about positive cloud to ground lightnings.

Here is a principle sketch from the above book about principles of lightning location in a thunderstorm.

RHABE

It would be unusual for a jetliner to be victim of lightning strikes.

Big sparks are cool. Makes me want to play with my HV transformers.

I used to work on Regulated 5 and 10 kV supplies and when there was a snapping sound from a newly manufactured one everyone looked toward me to make sure it wasn't me that was getting snapped.

"How much current for how much time will be needed to lower the strength to failure?"

Aircraft fly around for many years without lightning related skin weakening and failures.

The "clouded theory" has to do with which way discharges move.

The invisible lead and the following jump and resultant flash caused by ionization of atmosphere is noted.

Even ions from the Sun grabbed by the magnetic poles of the earth produce visible effects.

The ping pong action has to do with the charge reversing the polarity between the clouds. Chain lightning is caused by each discharge adding more electrons to the neighbor and the neighbor having been boosted discharges to the now less charged next neighbor cloud.

A postive cloud is simply a cloud that is less negatively charged than the one used for reference. If the positive cloud was your point of reference, the other would be a negative cloud.

"positive cloud to ground lightnings". I would think it would be Positive cloud FROM ground lightning.

If the cloud is more positively charged than the ground then the lightning would jump FROM the ground to the cloud.

A lightning arrester made with polished spark gap plates will tell which way the charge went. Pitting on the plate that received the blast indicates the direction the discharge came from. That's the simple way.

In the old days we used that method to determine the correct polarity connection of our ignition coil to prevent burning up the center electrode of our sparkplugs. We put a polished end of a carpenters pencil between the HV spark wire and ground leaving a small space on each side. The pitting on the HV spark wire side would indicate that the polarity was correct and it would be a long time before regapping the plugs would be required.

Hi, see my comments in-between your lines:

It would be unusual for a jetliner to be victim of lightning strikes.

You are right, very unusual but existing.

Big sparks are cool. Makes me want to play with my HV transformers.

Good idea, what about Tesla transformers?

I used to work on Regulated 5 and 10 kV supplies and when there was a snapping sound from a newly manufactured one everyone looked toward me to make sure it wasn't me that was getting snapped.

"How much current for how much time will be needed to lower the strength to failure?"

Aircraft fly around for many years without lightning related skin weakening and failures.

Very big lightnings are very rare. And under usual circumstances a pilot never will fly through a 17Km (50.000ft) high reaching thunderstorm nor nearby . So I cannot calculate the risc.

Have a look once more to post 174, this seems to be considerable damage to the skin.

The "clouded theory" has to do with which way discharges move.

And with the charge generation and separation.

The invisible lead and the following jump and resultant flash caused by ionization of atmosphere is noted.

Even ions from the Sun grabbed by the magnetic poles of the earth produce visible effects.

The ping pong action has to do with the charge reversing the polarity between the clouds. Chain lightning is caused by each discharge adding more electrons to the neighbor and the neighbor having been boosted discharges to the now less charged next neighbor cloud.

I suppose that this is an inductive effect from the very big current having stored much energy in its magnetic field.

A positive cloud is simply a cloud that is less negatively charged than the one used for reference. If the positive cloud was your point of reference, the other would be a negative cloud.

Reference potential is earth-potential. Clouds start to form nearly uncharged. Splitting of water droplets and hits of ice particles against each other generate and separate the charge. Existing electrical fields help in the separation.

"positive cloud to ground lightnings". I would think it would be Positive cloud FROM ground lightning.

Yes, same I do, but it is an established manner of language, so how to change?

If the cloud is more positively charged than the ground then the lightning would jump FROM the ground to the cloud.

A lightning arrester made with polished spark gap plates will tell which way the charge went. Pitting on the plate that received the blast indicates the direction the discharge came from. That's the simple way.

How do you know that no back and forth lightnings existed?

In the old days we used that method to determine the correct polarity connection of our ignition coil to prevent burning up the center electrode of our sparkplugs. We put a polished end of a carpenters pencil between the HV spark wire and ground leaving a small space on each side. The pitting on the HV spark wire side would indicate that the polarity was correct and it would be a long time before regapping the plugs would be required.

RHABE

Me: Along with turbulence ripping off parts, that's a real good reason for avoiding sparky places.

You: Good idea, what about Tesla transformers?

Me: I did one when I was young. Model T Vibrator box and all. It was a short lived experiment as we didn't have electricity and batteries were hard to come by.

You: "How much current for how much time will be needed to lower the strength to failure?"

Me: Lightning currents have a very fast risetime on the order of 40 kA per microsecond. Hence, conductors of such currents exhibit marked skin effect, causing most of the currents to flow through the conductor skin. The effective resistance of the conductor is consequently very high and therefore, the conductor skin gets heated up much more than the conductor core. A good conductor of heat disipates it well and aircraft at high altitudes are usually at very low temperatures. My last flight was at a temperature of - 65 F.

Me: Aircraft fly around for many years without lightning related skin weakening and failures.

You: Very big lightnings are very rare. And under usual circumstances a pilot never will fly through a 17Km (50.000ft) high reaching thunderstorm nor nearby. So I cannot calculate the risk.

You: Have a look once more to post 174; this seems to be considerable damage to the skin.

Me: The lightning struck the radome where the weather antenna is located, and has caused damage that "looks" quite dramatic. The most common problem found is usually moisture content in the radome. A lightning strike to an internally moist radome can be like knocking the bark off of a tree. Radomes have antistatic coatings too. I wonder how it god that dent in the nose.

Me: Dec 8, 1963: Pan Am flight 214 crashed as result of a lightning strike, and 81 people were killed.

Dec 24, 1971: Lansa flight 508 crashed as a result of lightning in Peru, with 91 people killed.

Me: The "clouded theory" has to do with which way discharges move.

You: And with the charge generation and separation.

Me: Yep.

Me: The invisible lead and the following jump and resultant flash caused by ionization of atmosphere are noted.

Me: Small rockets are sent up feeding out a long fine wire to discharge lightning at launch sites. Experiments with high powered LASERS have been going on to create leads for lightning discharges.

Me: The ping pong action has to do with the charge reversing the polarity between the clouds. Chain lightning is caused by each discharge adding more electrons to the neighbor and the neighbor having been boosted discharges to the now less charged next neighbor cloud.

You: I suppose that this is an inductive effect from the very big current having stored much energy in its magnetic field.

Me: I go with the idea that lightning, being so rapid that it loses much energy in the form of electromagnetic (radio) waves that there may not be as much retained magnetic field to be so effective that way.

Me: A positive cloud is simply a cloud that is less negatively charged than the one used for reference. If the positive cloud was your point of reference, the other would be a negative cloud.

You: Reference potential is earth-potential. Clouds start to form nearly uncharged. Splitting of water droplets and hits of ice particles against each other generate and separate the charge. Existing electrical fields help in the separation.

Me: As the subject is atmospheric lightning's effect on aircraft I tend to lean toward that. At high elevations with very low temperatures ice particles generate charges more easily. Water droplets interacting with dust particles also cause charges.

Me; "positive cloud to ground lightnings". I would think it would be Positive cloud FROM ground lightning.

You: Yes, same I do, but it is an established manner of language, so how to change?

Me: Old dog new trick. I know what you mean. It is the discernment discipline.

Like an adjustable spanner is call a Crescent Wrench even when it is not made by Crescent Tool company.

The ladies on an assembly line called cable ties Panduits. (Often called Zip ties because of the sound made when adjusted. Like the man zipping his fly or when a cop uses them for backup handcuffs). Panduit makes a variety of devices so I got a handful of various items made by Panduit such as cable management accessories power connectors and Various wire terminals, Butt Splices, Parallel Splices, Ferrules and a Crimping Tool all made by Paduit. I put in some of the same items made by other companies too. Their eyes crossed from data overload.

Me: Lightning arrester made with polished spark gap plates will tell which way the charge went. Pitting on the plate that received the blast indicates the direction the discharge came from. That's the simple way.

You: How do you know that no back and forth lightnings existed?

Me: Ping pong effect would cause both surfaces to be pitted.

An L C tank circuit in the sky. Cool.

I would like to see how researchers go about high speed recording of optical and electromagnetic effects of discharges. Like a phased array electromagnetic detection system that could tell if the discharges are from reversing polarities or a series of mono-polar discharges.

Your thoughts are maybe near to reality in some points, but in one point I am pretty sure (and previous posts support this completely) that you are completely wrong! Sorry.....

Aircraft are hit by lighning almost every day of the year, somewhere on this planet. I myself was in a 707 in '65 and we were hit 4 or 5 times in the space of 10 minutes or so, over Switzerland on our way from Frankfurt to Beirut and onwards to Singapore.....the aircraft was completely undamaged......later just before Singapore we were hit again a couple of times......

My guess/theory is that as the aircraft skin forms a a Faraday's Cage, the current is then distributed over a large area.......but I could be wrong of course.....!

Hi,

I agree that erroneous speed measurements are more likely to cause a catastrophic failure.

But with the lightnings: the ordinary lightnings normally don't do harm (in rare events there are problems) but these very rare lightnings from the positive cloud (upper cloud level) are so much more powerful that there will be a lot of damage.

You are right about the aircraft skin acting as a Faraday-Cage but the currents in the shield has to be low enough not to cause critical heating. (Or the conducting structure so thick that there is no critical heating.)

At any region of higher than usual resistance there will be extra heating.

There are also the effects of rising resistance with temperature (0.4%/K) and the skin effect that is limiting the current to flow in the outermost parts of the metallic conductor.

Hopefully we will know with certainty what happened.

RHABE

RHABE, thickness actually doesn't count for squat. in the case of a lightning discharge the waveform is of a very fast rising pulse, therefore the skin effect comes into play. It doesn't matter how thick the skin is, the current will only flow on the surfaces.

Interesting conversation.

I was involved in NASA Langley aircraft lightning studies years ago, from the aircrew side. Apparently, with composites making great strides in aircraft construction, studies have been resumed with new imperative.

See Here

Hooker

love to see how many of the (12) static wicks needed to be R & R 'd after that flight...

or , if the apu suffered a failure. maybe an over temp on the apu ? triggering an auto shutdown ? certainly looks like the apu exhaust gets lit up there.

again, i'm not adamant on the insistence that lightning caused this tragedy.

imho: with what we know: i was going to offer a scenario..

but at this time , i'll pass.

further speculation , imho : dosen't provide the families of this tragedy any comfort.

Please feel free to correct me if I'm wrong, but the APU on that 747 should not have been operating in flight.

On Chinooks we shut down the APU as soon as we got the engines up to flight rpm. And the DHC-8 I'm currently dealing with has landing gear extension sensors that will shut the APU down as soon as it leaves the ground.

That said, I don't have a clue what caused that flare you point out.

Hooker

Hi Hooker

no set standard for apu op's.

some a/c inhibit apu op's at altitude , other allow for the generator backup,..

yes weight on/ off wheels,..

kinda leaning towards customer requirements, since the same apu can be used on multiple a/c.

sometimes, fuel puddles in the apu exhaust " plumbing"...iirc, the newer apu's don't get that as much. iirc : the apu duty cycle did have some " motor " time to help clear any fuel puddling ...

once upon a time, i read where the " color " of the " flare " might lead to its origin.

but, i don't remember, so i can't reference that article, little more than rumor from me then...don't know what " color " skydrol " would show, or if the winter time operation shows anti-ice fluid, or if it's fuel , oil from the apu compartment..

can't think of any other fluids.. lav tank water, .. but that , if open , would have been visible before and after the strike...and its blue

The primary purpose of an aircraft APU is to provide power to start the main engines. Turbine engines have large, heavy rotors that must be accelerated to a high rotational speed in order to provide sufficient air compression for self-sustaining operation. This process takes significantly longer and requires much more energy than starting a reciprocating engine. The amount of energy required is far greater than what could be provided by a storage device (battery) of reasonable size and weight.

An APU solves this problem by powering up the aircraft in two stages. First, the APU is started by an electric motor, with power supplied by a battery or external power source (ground power unit). After the APU accelerates to full speed, it can provide a much larger amount of power to start the aircraft's main engines, either by turning an electrical generator or by providing compressed air to the air turbine of the starter motor.

APUs also have several auxiliary functions. Electrical and pneumatic power are used to run the heating, cooling, and ventilation systems prior to starting the main engines. This allows the cabin to be comfortable while the passengers are boarding without the expense, noise, and danger of running one of the aircraft's main engines. Electrical power is also used to power up systems for preflight checks. Some APUs are also connected to a hydraulic pump, allowing maintenance and flight crews to operate the flight controls and power equipment without running the main engines. This same function is also used as a backup in flight in case of an engine failure or hydraulic pump failure.

Yep, the A-330 that Sully belly flopped into the Hudson still had it's APU running which was fortunate because with neither engine generating power and the airspeed too low for the emergency ram-air to generate adequate power, he would have had zero control to do a controlled ditch had he not had his APU running still. Yet another "benefit" of FBW.

I understand Honeywell got a "thank you" for that one.

And well they should have! Honeywell saved over 200 lives that day.

I am not clear on the typical after-takeoff checklist for an Airbus, but on Boeings, the APU is usually shut down before pushback. Is it typical for an Airbus to keep it's APU running after take-off? or did Sully just get lucky that they had not shut it down yet?

I noticed that some planes have an engine or two running before pushback and others crank them up on APU power after pushback.

I flew on a Boeing and an Airbus on my trips in April & May.

I'm not sure where APUs come into any scenario as concerns this breakup.

Only way I can see that an APU might have any bearing is if it's inlet and outlet created a vulnerability in the aircrafts structure, or skin.

I am not familiar with the Airbus.

On a GII, the APU is not far from the tail, and is a hole in the plane.

As in simple carpentry where you frame around holes in the wall, or put headers up for open spans, I'd expect some beef to the airframe where the intakes and outs for the APU were.

The orders of my interest in causes are tailplane control, tailplane integrity, cockpit windshield, then windows again, then engines, then maybe this issue of the APU, though not at all on any explosion from its being fired up, but from any flaw in the airframe integrity that might have allowed the airframe to be fractured enough for the reported decompression.

Did this plane fly into a Thunderstorm, or not?

There was still a big storm in that location the day after the crash.

Hi R.

yes I agree and lightnings are fast but I don't know the current/time characteristics.

But if you consider considerable heating and 0.4%/K TC of resistivity and very likely intense current concentrations around sharp edges, bends, bolts and cracks - then I am not sure about the heating/melting behaviour.

I heard from experts about these 100mm masts of Al that were laid down with partially molten regions.

Maybe the self-regulating mechanism - hotter sections carry less current - may explain this, or these very long-distance lightnings have other impedance characteristics than the shorter ordinary ones?

Maybe also: molten material is partially evaporated (similar to some laser heating processes), spraying around any molten material, leaving a new surface which in turn will melt and spray?

If GW to TW (10⁹ to 10¹² W) is concentrated into a thin layer) then heating will be pretty fast. To calculate or estimate the current/time characteristic would be needed.

RHABE

Tail section.

My own personal theory is that the aircraft speed sensors (pitot tubes) packed up completely in the storm and the resulting problems caused either the crew or the flight computer to overstrain the stabiliser and it got wrenched off......in spite of program changes to that computer that are supposed to stop such happenings.....

If true, then Airbus will have to do some further redesigning again!!!

Agreed, like actually addressing the structural problems of the Vert. Stab. instead of trying to fix it in software.

Perfectly put to my mind.

(at least until we know more exact details!)

I think you can at least partially attribute this to the differing design philosophy on how FBW is implemented between Airbus and Boeing. Airbus, wants the computer to be in control of the aircraft, the pilot tells the computer what he wants and the computer is tasked with making sure the pilot is not asking the airframe to do anything it cannot handle. To do that, the computer is programmed with maximum values that may not be exceeded, but you can go right up to the maximum without any feedback to the pilot that he is reaching the maximum. But that means that in order for the airframe to stay in the safe region at all times, the system will never allow you to exceed 100% of the design minimum, regardless of what the consequences might be if you didn't, as a hard software limit. that means that any safety margin that might have been built into the design is unusable. Boeing's philosophy is that the FBW system should warn the pilot that what he is asking the aircraft to do exceeds the design limits of the airframe but allows the pilot to continue with the maneuver up to and until something breaks, then it tries to assess how much control is still available and adapt to the new control laws available to it. Which means that the pilot has full use of any safety margin that may be built into the system. And the limits are "soft", not hard. The wheel and yoke that the 777 still has is outfitted with force feedback systems so that the pilot can "feel" the airframe and "fly by the seat of his pants" if the situation warrants it. The airbus side stick has no force feedback, so the pilot has lost his tactile sense of what is going on with the aircraft.

Between your theory and the "inertia sensor", and the auto dive program that apparently cannot be overridden, plus altitude, temp, thunderstorm with the possibility of hail, pitot tubes of some reported flaws we can create a scenario where all minor flaws conspired to create a major disaster.

Irregular speeds have been recently reported that could well have been real events in a thunderstorm even if the pitot tubes were not frozen up.

Decompression inflight is reported.

No Mayday call from the cockpit.

Now I shall attempt to pivot our investigation from what to me is the most dramatic evidence, that being cabin pressure decompression reported automatically during flight.

What time did that happen?

Where exactly was the aircraft when that happened?

In turbulence, what is typically the weakest part of any aircraft structure?

Could the horizontal stabilizer on this aircraft have been broken off, causing decompression, and a completely out of control dive?

Now I have seen a picture of the vertical stabilizer, which did not look to be hail dented.

If we find hail dents we might have to look to the front of the plane on the slim chance that the Cockpit Windshield was somehow broken.

Imagine you are going 500 miles and hour, up and down and the windshield comes apart?

We will get evidence from the Vertical Stabilizer of great value, for if the horizontal tailplane was torn off, there will be evidence.

One thing that has influenced my posted thoughts were reports of V Tail Bonanzas, that lost control when the tail would sometimes be forced to essentially fold up, leading to a more common desire for the Debonair, which had a stronger and more conventional tail.

As well most of my time was in a Tomahawk, which was known to have a weak tail, and eventually I believe in later models more rivets were used. It was discomforting to look back at the tail of a Tomahawk which could well be wagging around in even the slightest of turbulence.

Further my first job at an airport became open after some of the line men were killed when a bolt fell off in the tail of a Cessna Conquest, and the plane went straight up and then straight down.

It is common for mechanics who have done some repairs to a plane to go for a test flight before giving it back to the owner, and I've been on some myself.

I have a particular rememberence of a ride in an old Hawker Siddley.

- and there is more.

Just sitting on the ground, I have seen where lighting will strike a plane. I saw a real nice jet that was hit in the tail while sitting on the ground, and the lighting blew a watermelon sized charred hole at the top of the vertical stabilizer.

Moving in the air of course is a different scenario, but it still adds to my typical view that the weakest most vulnerable part of most any aircraft is the tail.

Well then the Comet was brought down by square windows...

If the tail is cleared then we go to the windows.

What say you all?

I doubt you will see any "dents" in the Vert Stab since it is an all-composite structure. You might find delam in places where it took a good hit, but unless you hit it hard enough to break it, the damage won't be visible.

Your point is taken.

Still you leave a place to look by mentioning delam.

Seems like if they did get into a large hailstorm, in a thunderstorm, even a hailstone would need to be as large as a frozen chicken, to break the windshield, or tear the tail apart. A baseball sized hailstone could tear off even the most robust of pitot tubes.

No point now for me to repeat myself.

What order of inquiry to possibilities do you think most productive?

Since the only things we currently have in our possession to look at right now are the bodies, the telemetry and the Vert. Stab., I think I would be looking at the telemetry record for additional clues given what we now suspect, look at the bodies to see if they underwent explosive decompression at altitude or if they died of blunt force trauma, or if they died from drowning. and finally I would be looking at the broken surfaces of the Vert. Stab. for clues as to how much lateral G-loading the tailplane underwent (and what parts need to be reinforced to increase the G-loading capability in future airframes as well as ideas on how to reinforce the existing airframes. Once we find the FDR and CVR (if we find them, and I'm cautiously optimistic on that.) we'll have a lot more data to work with. Barring that, if we can find more of the structural parts, we should have more data to use to reassemble a timeline.

Good point about looking at the bodies.

Between the bodies and the Vert. Stab., a timeline is established, don't you think?

-at least as far as the short span indicated between difficulty and breakup implied by no pilot captain transmission from the cockpit.

Evidence is everything.

Yes, in broad terms. If the Vstab broke from lateral forces (as you's expect from either too much rudder applied at speed, or from sudden gusts) you'd expect to see different pattern of damage than if it broke from axial forces (such as impacting the water).

The bodies should be able to tell if they lost pressure at altitude, if they died from blunt trauma/excessive g-loading or if they drowned or burned.

Of the three, the bodies will probably tell most of the tale.

You are right that between the bodies and the condition of the tail, without a black box we ought to be able to figure out what happened.

I wouldn't go quite that far. We might know that the tail came off in flight but the reason it came off won't be known without the FDR and CVR. Did the plane yaw radically because one engine failed causing the aerodynamic loading on the tail to exceed structural maximums? or did one of the pitot tubes ice up and give the FCC a false indication of severe sideslip? Or was there an F5 embedded in the line of thunderstorms that ripped the tail off? Is weather radar data recorded on FDR's? I doubt it but I don't know for certain.

We might be able to know in general terms WHAT happened, but we really need to know WHY it happened.

Lets all place our bets and wait and see if enough evidence can be found to make a conclusion......

no, i can't imagine a scenario where the windscreen is shattered by lightning , other than in Hollywood.

construction of the windscreen specifically addressed this issue. triple pane , vacuum chambers, etc.

the mount bolts fixture's were not visible in any photo i've seen. see previous posts for estimation of tail fin separation. and loss of yaw control, well ,,,

now, as to rapid decompression at altitude. sto in the trainer.

the idea that the structure of the tail section is only composite material is incorrect.

panels or sections may be mounted to frames , stringers ,etc, those are not composite.

hope that helps

"that being cabin pressure decompression reported automatically during flight.

What time did that happen?

Where exactly was the aircraft when that happened?"

Hi,

altitude was very likely near 11000m if not changed a lot by up-down-streams.

Time is unknown.

Thunderstorm was (upper cloud level) 17000m that is 50000ft!

This was a giant thunderstorm, I never realised that the planes are not able to reach this level to pass above!

And how much above is suitable to avoid the turbulences that certainly exist above?

RHABE

On the topic of lightning, and nothing to do with AF447, a RNZAF Orion was hit by lightning over Canada on Monday 8th June, in joint exercises.

It left a "little" scratch

lovely view of the " lower 41 " area .

But the aircraft made it back and landed safely too...

It looks like a "Hitler 'tache"!

Looks like it tried to sniff the pack leaders APU.

A similar thread has been going on here. They claim to have a transcript of the last transmissions, but I do not read french well enough to translate.

http://www.eurocockpit.com/

http://www.chron.com/disp/story.mpl/front/6477191.html

Took a look.

Been in an Piper Aerostar on a check run that saw the rabbit and hit the ground.

1/16 mile visibility.

Awhile back I did some research on Learjet crashes as reported by the FAA.

Somebody will do anything.

Hi,

most important link!! GA.

Look at the report from one pilot that experienced on the same route a sudden stall by flying into a big blob of unusually warm air, this was once in 40 years of experience only, but we will have to consider rare events.

So warm air, tail winds will both be dangerous: not enough velocity.

If this is additionally mixed with severe turbulence (some g acceleration up and down, up and down velocity up to 700 m/min!), and thus the necessity to switch off the auto-thrust and autopilot, the necessity to go on a sudden dive to regain velocity and/or denser air this in total would add up to a potentially catastrophic failure of the plane by mechanical overload.

RHABE