Air France Jet Crash: Are Commercial Jets Safe Against Lightning?

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The discussion centers on the safety of commercial jets against lightning strikes, particularly in light of the Air France jet crash in the Atlantic, which initial reports suggested might have been caused by lightning. While commercial aircraft are designed to withstand lightning, concerns were raised about potential structural damage and electromagnetic interference. Experts noted that lightning strikes are common, with planes being hit at least once a year, yet they rarely result in catastrophic failures. The conversation also touched on the challenges of predicting damage from lightning and the possibility that other factors, such as severe weather or mechanical failure, could have contributed to the crash. Ultimately, the exact cause remains uncertain, pending further investigation and recovery of the black box.
  • #51
Mech_Engineer said:
I don't hydrophones will be very useful in finding a black box under water, unless it sending out a sonic signal.

That's what they do.

http://en.wikipedia.org/wiki/Underwater_locator_beacon

Edit: mgb already answered while I was googling.
 
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  • #52
mgb_phys said:
This was the cause of a loss of a 737 a few years ago where a blocked coffee machine had been ripping coffee onto them for years unnoticed until they shorted out.
:bugeye: I thought that's what regular maintenance checks were for!
 
  • #53
DaveC426913 said:
:bugeye: I thought that's what regular maintenance checks were for!
You would have thought so!

Actually I had slightly misremembered. The coffee drain took out all the power on a Quantas 747 but it made a safe landing http://catless.ncl.ac.uk/Risks/25.02.html#subj1
 
  • #54
mgb_phys said:
It's possible to have damage caused by very localised win shear, where one wing is being pushed up and one being pushed down. Small planes have been flipped over by this in say wake turbulence. But generally the change in pressure happens on scales larger than the wing chord so the entire lifting surface is being pushed down - which is much lower stress.

You're flying an airliner at cruise speed with a 5 degree angle of attack and enter a region of air with 150 of so mph vertically downward velocity, changing your angle of attack by -17 degrees. Now you are flying with negatively loaded wings at an angle of attack of -12 degrees nearing or surpassing the negative stall CL. The lift coefficient would be around -1.0 accellerating the aircraft downward at 1.4 gees. This is roughly the behavior of a wing built on the 747A315 section.
 
  • #55
mgb_phys said:
Almost all nosecones are made from some sort of composite. They house the weather radar and putting your radar antennae inside a faraday cage has performance issues.

Good to know. I only had common sense to go by.

True but irrelevant, the individual avionics and the wiring is very well shielded.
The main issue with composite airframes and lightning is electrically bonding panels together, if there is a break in electrical continuity between a panel that is hit and an adjacent one you get arcing which leads to damage.


'Very well shielded.' What does this mean? How well shielded and against what kind of electrical faults; static discharge, or induced current discharge? How many volts and how many volts per seconds compared to the values lighning obtains? It's relevant until this values are know, then perhaps still relevant.

The avionics racks are under and behind the cockpit as on most planes. This was the cause of a loss of a 737 a few years ago where a blocked coffee machine had been dripping coffee onto them for years unnoticed until they shorted out. The original 737 also had a problem with toilet cleaner leaking into them. They are better protected on later models.

I looked for quite some time to find where avionics 'n stuff were located in the A330 or any Airbus. I came up empty. Thanks for the useful info.
 
  • #56
Phrak said:
I looked for quite some time to find where avionics 'n stuff were located in the A330 or any Airbus.

: backs very carefully away from Phrak, deletes all correspondence linking us :
 
  • #57
Perhaps out of this event, someone will design a cushion for black boxes that will allow them to float rather than sink - something along the lines of the cushions that were used for the Rovers landing on Mars. It would seem advantageous to have black boxes in a buoyant protective cushion.
 
  • #58
mgb_phys said:
I meant that it wasn't the wind that blew the stabilzer off, the pilot turned it full to the sie while flying along at several hundred mph.
I know, I wasn't suggesting that either - the pilot overreacted to an attitude change due to wake turbulence.
It doesn't try, the software detects very rapid movements and let's them happen - it's better to be moved off course or off altitude briefly than waste fuel and stress the airframe by fighting every gust.
If the gust is a 100mph updraft (the media is reporting they were in the area at the time) and the computer doesn't react fast enough, the wings get ripped off.
It's possible to have damage caused by very localised win shear, where one wing is being pushed up and one being pushed down. Small planes have been flipped over by this in say wake turbulence. But generally the change in pressure happens on scales larger than the wing chord so the entire lifting surface is being pushed down - which is much lower stress.
You're still not getting what I'm saying: the wind does not need to be up on one side and down on the other to rip the wings off.

Entering a localized 100 mph up or downdraft hitting the wings causes a very rapid acceleration, whether the pilot/computer reacts to it or not. Sure, the wings can withstand such a distributed load and rapid acceleration - but they are connected to an airplane. The wings cannot accelerate the airplane up/down that fast without ripping the wings off at the root.

We aren't talking about mere rough air here, where you can look outside the airplane and watch the wings flap up and down a few feet when flying through it. This is a large, rapid, and sustained, change in the direction of the relative wind across the wing: a large change in angle of attack and large change in the lift generated.

Did you look at the plane crash I gave info about where an A-4 flew into the area later and experienced spontaneous +9 and -4 g accelerations and a loss of control due to the updrafts? The airliner that crashed was ripped apart by the effect of the updrafts alone.

It isn't all that rare that sever turbulence thows people against the ceiling of an airliner.

In any case, different news sources are talking to different experts and thus favoring different theories. USA Today's expert is theorizing about exactly what I said - an updraft tore apart the plane. The CNN expert is favoring the lightning theory.
 
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  • #59
Astronuc said:
Perhaps out of this event, someone will design a cushion for black boxes that will allow them to float rather than sink - something along the lines of the cushions that were used for the Rovers landing on Mars. It would seem advantageous to have black boxes in a buoyant protective cushion.
That's not enough - they also need to find their way out of the plane. There have been some articles about that in the news due to this crash.
 
  • #61
russ_watters said:
They are also saying some pilots reported seeing something consistent with a plane exploding and dropping to earth.
Perhaps that could have been lightning. Out there, the flights are at 34000+ feet.

I've flown in puddle jumpers past lines of thunderhead and at the base, it looked like blasts of light. There was also lighting above us, to the side and below us.


I think there was a Spanish flight in the vicinity.


It also reminds of the flight in South or Central America where a Boeing 737 encountered severe turbulence. The storm apparently caused the plane to roll sharply, and the crew overcompensated and rolled the plane upside down, or well beyond design. The plane ultimately nose-dived into the ground.
 
  • #62
DaveC426913 said:
: backs very carefully away from Phrak, deletes all correspondence linking us :

Ha! :eek: It took some good amount of time for me to figure what you were talking about.
 
  • #63
russ_watters said:
Entering a localized 100 mph up or downdraft hitting the wings causes a very rapid acceleration, whether the pilot/computer reacts to it or not. Sure, the wings can withstand such a distributed load and rapid acceleration - but they are connected to an airplane. The wings cannot accelerate the airplane up/down that fast without ripping the wings off at the root.
Yes I think I was missing your point.
Severe turbulance can do serious damage to a plane, although large planes aren't accelerated as violently as the small skyhawk.
The china airlines flight where the crew stalled and rolled a 747 had most of the tail ripped off - it's easily possible that severe turbulence tore a control surface or part of a wing off. Generally turbulence isn't a problem because planes avoid it - if they couldn't because there was no way around the storm, or the storm was much more violent than they thought then it is a very likely cause.

I used to fly to S America frequently and it does get very 'interesting' over the equator even without storms
 
  • #64
I can't find the maxium G loading, nevermind + or - , for the A330-200. How do you search for it anywho?
 
  • #65
mgb_phys said:
Yes I think I was missing your point.
Bizarre, you keep ignoring the example I gave. Maybe the third time's the charm:
While flying into the wind, approaching Mount Fuji from the downwind side, the aircraft encountered severe clear-air turbulence associated with lee waves, causing a sudden structural failure that initiated the in-flight breakup sequence. At the time of the accident, winds at the summit of Mount Fuji were measured at 60 to 70 knots from the northwest. Lenticular clouds associated with lee waves were observed on weather satellite photos taken 30 minutes before the accident some 240 km (150 mi) to the south, but were not visible in the vicinity of the accident where the skies were clear.
http://en.wikipedia.org/wiki/BOAC_Flight_911

This is exactly what I am suggesting may have happened to the Air France flight. The plane in the incident above was literally ripped apart by a vertical wind event.
although large planes aren't accelerated as violently as the small skyhawk.
True, but given the magnitude of the acceleration the Skyhawk felt, it would only need to be about half as much to break up an airliner. In any case, there is no need to argue that point or this issue of whether it can happen at all: it actually happened. We know it is possible for a vertical wind event to rip apart a large airliner because it has happened before.
 
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  • #67
russ_watters said:
According to this article, it is 2.5*150%=3.8g

http://www.aviationtoday.com/av/categories/atc/13015.html

Well done! I don't know how I managed to pick the wrong keywords.

"For example, the pilot is not allowed to exceed the airplane’s 2.5-G design load, even though a 50% safety factor is built into the structure, suggesting that the airplane is strong enough to pull 3.8 Gs."

This hints that the airframe was distructively tested and failed at 3.8 Gs positive when spanking new, and Airbus decided to limit, via software, the pilot's ability to pull more than 2/3's of this, and perhaps quotes the 2.5G value as their specifications to purchasers.

From various insudry sources I've noted, the pilot shoud reduce airspeed by about 25 knots on the expectatation of turbulent atmospheric conditions. This is little compared to the cruise speed. The dynamic forces are recduced by 10%.

3.8 is a very nice number and should be encountered not far from stall angle of attack. This means that the wings won't ever encounter more than 3.8 Gs before stalling, or very little above it.

What this means is that they could still rupture on a 4 year old airframe with the right amount of shear.
 
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  • #68
russ_watters said:
That's not enough - they also need to find their way out of the plane.

I recall reading somewhere that there are planes where black box is mounted in such a way that it gets ejected by inertia on impact. Doesn't sound difficult to manage.
 
  • #69
I think it was mentioned earlier, but one pilot saw an intense white flash, extending vertically to the ground and lasting around 6 seconds, at the time the plane disappeared. Positive Lightning?
 
  • #70
Interesting discussion here - http://en.wikipedia.org/wiki/Coffin_corner_(aviation ). The plane could have stalled, dropped precipitously, and perhaps achieved beyond design load conditions.

http://en.wikipedia.org/wiki/Lee_waves#Aviation


With cumulonimbus clouds, there can be significant up and down drafts.


Then there is this: Could a Computer Glitch Have Brought Down Air France 447?
http://news.yahoo.com/s/time/20090604/wl_time/08599190290700

Could the lightning have caused ADIRU failure or failure of multiple systems while the aircraft simultaneously encountered severe turbulence?
 
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  • #71
Been following this here

http://www.pprune.org/rumours-news/376433-af447-6.html

Fair bit of fact, good read.

Most speculation at the moment as any number, or any single thing could have caused this.

There has been no confirmed wreckage found, its all floating junk that's always in the atlantic so far.

One can refer back to the near miss with the QF A330 flight not too long ago, such a failure combined with bad weather, lossing WX and flying into the heart of a CB could have brought this plane down.
 
  • #72
herpamad said:
There has been no confirmed wreckage found, its all floating junk that's always in the atlantic so far.
Then there are conflicting reports. Some news articles are stating that some pieces of debris are confirmed to be from the Air France flight.
 
  • #73
Air France memo says it's replacing flight sensors
http://news.yahoo.com/s/ap/20090605/ap_on_re_la_am_ca/brazil_plane

Apparently there is concern that the pitot tubes iced up, and provided false information to the flight deck.
RECIFE, Brazil – An Air France memo to its pilots about the crash of Flight 447 says the airline is replacing flight-speed sensors in all its medium- and long-haul Airbus jets.

Air France declines to comment on the memo obtained by The Associated Press, saying it is for pilots only.

Airbus says the matter is part of the probe into the crash that killed 228 people flying from Rio de Janeiro to Paris.

The memo sent Friday says Air France has been replacing instruments known as pitot tubes and will finish in "coming weeks." It does not say when it started.

One theory of the crash is that the tubes feeding speed sensors may have iced over, confusing plane computers and causing the plane to fly too fast or slow in rough weather.

. . . .
 
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  • #74
One theory of the crash is that the tubes feeding speed sensors may have iced over, confusing plane computers and causing the plane to fly too fast or slow in rough weather.
All Pitot tubes have heaters. There was a spectacular crash of a stealth bomber on takeoff who forgot to turn the heater on (no idea why this should even be an option), there have also been a couple of crashes where tape was left over them after cleaning or a bird had stored nuts in the hole!

It's possible that the heaters failed or that icing was so bad it overcame them but the aircraft has multiple independant ASIs
 
  • #75
French nuclear sub was directed to the area.
 
  • #76
From the activities of Air France we might assume that either Airbus, Air France or both are concerned about possible pitot tube mis-performance--or clever misdirection, but people don't conspire, so nevermind that--however people do act in common cause :-p

http://www.auf.asn.au/groundschool/umodule2.html

(*The reason why CAS [calculated air speed] does not always correlate to aoa [angle of attack] is that when inertia and random displacement forces — atmospheric turbulence — come into play, aoa may change momentarily without a change in CAS.)

An ASI [air speed indicator] is an imperfect mechanical instrument which is subject to instrument errors. The associated pitot/static system is also prone to pressure sensing errors due to the positioning of the pitot head and the static vent relative to the airstream. That relative position changes as aoa changes. CAS is the airspeed after you have applied corrections to the IAS [international standard atmosphere] for those instrument and position errors occurring at that aoa in that particular aircraft. The measured corrections should be stated on a card placed near the ASI. You should also be aware that position errors may be quite significant, possibly 10 knots or so — particularly at high aoa or when the aircraft is slipping.

(My boldface and bracketed text.)
 
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  • #77
The problem with calculating airspeed is conflicting estimates. Available to the flight instuments are the the pressure reported by the pitot tubes, the vertical airspeed reported by variometers, angle of attack reported by the angle-of-attack sensors located on the leading edges of the wings, and the atitude and velocity reported by the inertial reference unit. This is agrevated by the possibility of failing instuments. On top of this there are distrubuted sensors on each wing.

Airbus has the algorithms in hand. They have the software, but not the hardware. They want the instuments in hand to see if they are damaged in any way. They can't obtain these from Air France 447, but they can examine samples from the fleet of Air France airliners. Air France has a monitary interest in reporting good news to their potential customers. Supplying pitot tube modules to Airbus for analysis should be in their best monitary interest. It is good for both parties should they be able to report: "problem solved". Corporate grubbers, you know, regardless of reality, if a happy ending in air saftey can stick in the public craw, go for it.
 
  • #78
Phrak said:
The problem with calculating airspeed is conflicting estimates. Available to the flight instuments are the the pressure reported by the pitot tubes, the vertical airspeed reported by variometers, angle of attack reported by the angle-of-attack sensors located on the leading edges of the wings, and the atitude and velocity reported by the inertial reference unit.
Why would these result in conflicting information? They don't measure the same thing. The only thing that measures airspeed is the pitostatic tube.
 
  • #79
russ_watters said:
Why would these result in conflicting information? They don't measure the same thing. The only thing that measures airspeed is the pitostatic tube.

There are several pitot tubes, each measuring/reporting different values. The pressure presented to the transducer in a pitot tube depends on on the air density as obtained from barometers or calculated from the inerital reference unit, and the direction of the airflow on both pitot head and the static vent.

The nominal airflow direction can be calculated from the inertial reference units (that calculate acceleration, velocity, displacement in space, and orientation with respect to a calculated horizon), angle of attack sensors, and variometers (for vertical airspeed).

To this, add GPS altitude data.
 
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  • #80
Phrak said:
There are several pitot tubes, each measuring/reporting different values.
Well, if one is damaged or coverd with ice, sure, but I would think the plane has the ability to compare and detect faults.
The pressure presented to the transducer in a pitot tube depends on on the air density as obtained from barometers or calculated from the inerital reference unit...
Yes, pressure depends on air density, but the critical "airspeed" for an airplane is indicated (uncorrected) airspeed. It doesn't then get corrected for local air density, because indicated airspeed, is what determines how much lift the wings produce. You wouldn't want it corrected, otherwise, you might find (for example) the plane would stall even though its equivalent airspeed (corrected for density) is well above stall speed.
...and the direction of the airflow on both pitot head and the static vent.
No, the pitostatic tube is mounted on its own little wing that ensures it is oriented with the correct angle of attack.

http://en.wikipedia.org/wiki/Airspeed

The nominal airflow direction can be calculated from the inertial reference units (that calculate acceleration, velocity, displacement in space, and orientation with respect to a calculated horizon), angle of attack sensors, and variometers (for vertical airspeed).

To this, add GPS altitude data.
No, they can't. The direction/speed of airflow can only be directly measured by the pitostatic tube. Those other sensors only tell you which way they plane is moving with respect to the earth. The key difference is they don't take into account wind. There is no conflict between these information sources because those other information sources aren't used in the way you are suggesting.
 
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  • #81
I don't know where to start. The pitot tubes don't measure wind direction. They do not read the same values under dynamic conditions, especially turbulence. There are triple redundant systems and algorithms at work. The flowchart for all these quickly grows into megabytes of code to consider the multiplicity of conditions from failures and faults.
 
  • #82
russ_watters said:
Well, if one is damaged or coverd with ice, sure, but I would think the plane has the ability to compare and detect faults.
Don't remember which one but I think one of the 757/767? crashes in S America was caused by a single blocked pitot tube, the crew saw conflicting readings but didn't know that the autopilot only took ata from one tube - unfortuantely in this case the blocked one.

Airbus issued an advisory basically just saying pay attention if you are in bad weather and the instruments give different readings.

It would be nice to have a way of measuring local airspeed that wasn't quite so dependant on the air conditions around the aircraft - but that might be a bit of a paradox!
 
  • #83
Phrak said:
I don't know where to start. The pitot tubes don't measure wind direction.
Have a look at the picture in the wiki. Notice that it is mounte on its own little wing on a swivel so it always points into the wind (at least in the pitch axis).
They do not read the same values under dynamic conditions, especially turbulence. There are triple redundant systems and algorithms at work. The flowchart for all these quickly grows into megabytes of code to consider the multiplicity of conditions from failures and faults.
I'm not sure what you are getting at here. What you seemed to be saying before is that if the pitostatic tube on its attitude swivel says the plane is flying at 200 kts with a 5 degree angle of attack but the gps says it is moving across the ground at 150 kts that that is a conflict that could be a problem in maintaining control of the plane. It isn't - that's a navigation problem (not a flight control problem) only.
 
  • #84
Have a look at the picture in the wiki. Notice that it is mounte on its own little wing on a swivel so it always points into the wind (at least in the pitch axis).

The wikipedia picture was not the best example of a pitot tube.
The picture in wiki is a pitot tube with an angle of attack sensor (the black "little wing" ) attached. The angle of attack sensor is a completely separate instrument and is only attached to the pitot tube (in that example) as a convenience for mounting.
 
  • #85
jgrenwod99 said:
Have a look at the picture in the wiki. Notice that it is mounte on its own little wing on a swivel so it always points into the wind (at least in the pitch axis).

The wikipedia picture was not the best example of a pitot tube.
The picture in wiki is a pitot tube with an angle of attack sensor (the black "little wing" ) attached. The angle of attack sensor is a completely separate instrument and is only attached to the pitot tube (in that example) as a convenience for mounting.
In the picture, though, it makes the pitot tube swivel to ensure that it points in the direction the plane is moving. They aren't separate devices.
 
  • #86
An airplane always moves forward (like an arrow) so the pitot tube is mounted so it points in a forward direction. Pitot tubes don't swivel. You may be assuming that the black disc at the base of the pitot tube mast swivels in some way, but it doesn't. What is movable on the pictured device is the black wedge shaped piece which is the angle of attack vane.
 
  • #87
I worked for an airline for ~10 years. Lightning strikes were common. Only once did I see an aircraft sustain actual damage from a lightning strike. It was a Dornier 328. A large chunk of the verical stabilizer was blown off at the tip. The fuselage was damaged along the entire length. It looked as if it had been hit with a spot welder. There were several holes in the aluminum, the largest about the size of a dime.

I've only ever seen fixed pitot tubes. Angle of attack sensors (obviously) swivel. In the wiki picture, the actual pitot tube (silver) is fixed.
 
  • #88
NateB said:
I've only ever seen fixed pitot tubes. Angle of attack sensors (obviously) swivel. In the wiki picture, the actual pitot tube (silver) is fixed.
Looks to me like it is part of the swivel, but if most are fixed, ok...
 
  • #89
Air France tail found; US helps hunt black boxes
http://news.yahoo.com/s/ap/brazil_plane

So hopefully they will recover the black boxes, as well as more of the craft, and well learn more details.
 
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  • #90
russ_watters said:
Have a look at the picture in the wiki. Notice that it is mounte on its own little wing on a swivel so it always points into the wind (at least in the pitch axis). I'm not sure what you are getting at here. What you seemed to be saying before is that if the pitostatic tube on its attitude swivel says the plane is flying at 200 kts with a 5 degree angle of attack but the gps says it is moving across the ground at 150 kts that that is a conflict that could be a problem in maintaining control of the plane. It isn't - that's a navigation problem (not a flight control problem) only.

I'm sure you're right. I'm sure the Airbus must use vaned pitot tubes. Three pieces of air data can be used to obtain corrected speed: the dynamic and static pressures, and angle of attack for off-axis corection--or the tubes might handle this on their own. The swivel is useful in negating the need for off-axis airflow around a verticle axis. I don't think yaw information is collected. I'll find out.
 
  • #91
Additionally, angular correction factors for the barometric pressure can be input to the ADIRU to quantify side slip. You would want this information because the area of the pitot tube normal to the airflow is proportional to cos theta. Pitot tubes can have static pressure inlets on horizontally disposed sides of the tube. The difference in measured barometric pressure between these two can be used to calculate yaw, or wind direction in the plane, as you have said. Or yaw angle could be obtained from transducers in the swivel. Either way should work with a fixed or swiveled pitot tube.
 
  • #92
How can one possibly ascertain speed by way of measuring an external, dynamic medium?

Regardless of algorithims, this is inherently flawed. There is NO WAY that anyone can tell me that algorithims are sufficient to compensate for, example, a sudden 100mph wind shear to accurately tell me how fast my plane is flying. Indeed, I have NO IDEA that the wind shear is actually 100mph other than a reference to the plane.

One needs a static reference point, independent of the dynamic medium the plane is flying through.
 
  • #93
pallidin said:
How can one possibly ascertain speed by way of measuring an external, dynamic medium?...One needs a static reference point, independent of the dynamic medium the plane is flying through.
But the dynamic medium is what you are interested in. Flying depends on the relative velocity of the wind over the aerofoil, the velocity of the plane relative to the ground is pretty irrelevant except to tell you how late you will be.
 
  • #94
mgb_phys said:
But the dynamic medium is what you are interested in. Flying depends on the relative velocity of the wind over the aerofoil, the velocity of the plane relative to the ground is pretty irrelevant except to tell you how late you will be.

OK. That makes sense. Sorry for my rant.
 
  • #95
Weather is a simpler explanation than lightning

Lighting strikes of air-craft are common and foreseeable. Though it is
quite likely the system will be disturbed its computers should reboot
quickly and enough come up to provide quorum in time. Some one I know
who flies Airbus has had some boot up anxiety when his aircraft was
struck coming into land. The system came up again and after having no
control the approach was no longer suitable for an instrument landing,
but still good enough for a manual landing. As the system was up he
wanted to get the aircraft down while it was still responding so he
performed a manual landing. It was then in the shop for lots of time
consuming diagnostics.

Aircraft used in Australia frequently cross the tropics so they are
fitted with radar that can detect inter-tropical convergence. The Air
France crash telemetry reported garbage which could mean that it may
have flown into this. The last burst of data could be from a fatally
damaged aircraft after it as flown into something that it could not
withstand.
 
  • #97
It sounds like aircraft flying in such conditions could do with a redundant GPS to determine speed, which could serve to alert the pilot/system that the pitot tubes may be giving erroneous data.

Aircraft used in Australia frequently cross the tropics so they are
fitted with radar that can detect inter-tropical convergence.
Perhaps such equipment (Doppler radar?) should be mandatory on ALL commercial aircraft flying through the topics.
 
  • #98
Astronuc said:
It sounds like aircraft flying in such conditions could do with a redundant GPS to determine speed, which could serve to alert the pilot/system that the pitot tubes may be giving erroneous data.
But the GPS gives you absolute speed whereas what you need is 'relative to the airflow' speed
 
  • #99
Yes - I understant that. I was thinking in terms of changes of speed and position. In theory the system would monitor for changes in air speed (assuming pitots are working properly) with changes in actual speed, and consistency in those trends.


Perhaps pitot tubes need so laser doppler anemometry as backup, or at least someway to determine of they are plugged or otherwise not operating properly.
 
  • #100
I think they already do a lot of filtering to ignore sudden changes in pitot readings.
the danger is if they gradually ice up and start reading low you don't know you aren't going into a headwind.
But you would have thought with enough of the units you could detect a trend, if 1 probe shows you slowing more than the other two then something is wrong.

Even a simple backup flow meter would be useful. I wonder if you could use the load on the engine fan? They are basically just 8ft diameter windmills !
 

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