Lu Zuckerman

To: A-310 and A-300-600 pilots.

I am writing a book and I need some technical assistance / advice. The book deals with the hypothetical crashes of two different hypothetical airliners. One aircraft suffers from a runaway flap system ending up in the flaps tearing away from the wings resulting in a crash. The second aircraft loses a large section of the left wing due to a fuel tank explosion resulting from a lightning strike and loss of the aircraft.

Here are my questions and please forgive me if I use incorrect terminology. Any corrections will be appreciated.

1) The pilot gets an indication on the (XXXXXX) that his flaps are moving and there is no command from the command sensor unit. Remember, if the computer did not command movement it can not stop it. The pilot shuts off both the yellow and green system and then turns one system on and if there is movement he turns it off and turns the other system on. This will work but is there and alternative and or better way to stop the movement? Where is the fault-displayed (XXXXXX)?

2) Several pilots have written up that EMI is causing problems with their electronics and it is noticeable during radio transmissions. The mechanics have not been able to determine the source of this problem. Can this happen?

3) You are on final and between you and the intended landing airfield there is a small storm with imbedded lightning. There are two other airports in the area with possibly conflicting traffic. Would you penetrate the storm or would you elect to enter into a holding pattern waiting out the storm realizing that to do so might result in the loss of your spot at the terminal? Landing on an alternate runway is not an option.

I may come back with additional questions.

Thanks for your assistance.

Please respond by PM in order to minimize the material on the PPRuNe server.



Note - while I applaud Lu's concern for server dyspepsia, I am more concerned that the rest of us might miss out on some good gen. Feel free to post your answers to the thread as you see fit ... and I'll fly top cover against head office incoming ...

JT

Lu Zuckerman

To: A-310 and A-300-600 pilots

If I don’t get any responses I will have to go along with my own assumptions.

1) Shutting off the hydraulic systems and not knowing where the error message is announced.

2) EMI has been written up

3) The pilot would penetrate the storm even though there was embedded lightning.

My answer may be incorrect but they help in the story line. If I am incorrect in my assumptions please do not contact my publisher telling him of my errors.

Bus429

Thinking about the Question 1)

Question 2) - EMI can occur and can be attributed to several causes - poor or degraded screening of cabling in the audio integrating system; poor electrical bonding or degraded connections of/in electrical consumer equipment - particularly reactive devices like electric motors and tacho-generators. Also poor static discharging can also cause problems. I've had to deal with the latter on light aircraft but never on a big one. I've dealt with the other defects on 757s and 737-200s.
Poor comms can also be attributed to problems with antenna feeders and actual antenna installations.

Lu Zuckerman

To: Bus429

In this particular case it is no electrical bonding of the flaps and slats to the airframe. Thank you for the input about RFI/EMI effecting the radio transmission. One down and two or more to go.

Bus429

All answers above were related to question 2 - I have not got my A300-600/A310 notes to hand!!

To remove all hydraulic power on an A300-600, a pilot would have to offload 4 EDP (engine driven pumps - 1 green system pump on each engine; and one each yellow and blue system pump). This highly unusual configuration would be brought to the pilot's attention visually via ECAM and aurally (probably a CRC).

I cannot with any certainty remember the config of the A300 hydraulic system. The yellow system, I think, also has an electric pump. This is used for cargo doors, among other systems.
Lu - please appeal for more information from other more knowledgeable PPRUNERs!!!

Lu Zuckerman

To: Bus429

In the scenario of runaway flaps it would only be necessary to turn off the green and yellow system not all of the hydraulic systems.

The annunciation I was alluding to was for the flap movement. Would that be on the ECAM?

If any of you have a question about how the flaps could move with out the FS Computer shutting it down I will respond to your questions and provide two illustrations.

Capt Chambo

I can't answer questions 1 or 2 as I only flew the A320/321 and not the A310 or A300-600, but the answer to question 3 is general airmanship.

In the case of your "small" storm with embedded lightening. I would be inclined to hold off. It's size will be apparent from your weather radar, and you might make an educated guess at it's possible duration. You will also have upper wind readouts from your FMC, this might help you to decide if the storm is remaining static, or whether it might be blown off the approach course.

As other aircraft will probably be making the same decision I would assume that "terminal spot pressure" will be eased. Practically there will probably be mayhem on the ground anyway as the departure rate will also be slowed by the same storm!

Remember of course that a lighthening strike is spectacular but not necessarily dangerous for an aircraft or it's occupants. The fuselage being electrically bonded means it acts as a Faraday cage

Lu Zuckerman

To: Capt Chambo

This is true for all other aircraft however on these two particular aircraft the flaps and slats are not electrically bonded to the wing. It may also be true for other aircraft made by this manufacturer if the corporate mentality of the suppliers of associated equipment hasn't changed.

Aircraft are being struck on a daily basis so it indicates that aircraft are flown in storm cells with embedded lightning. Is there any situation where the slats can be extended when flying in this situation?

Capt Chambo

I bow to your superior knowledge of the A310 and A300-600 series. I recall your previous posts as to the (alleged) design limitations of these aircraft, and the reservations that you have expressed to designers and manufacturers.

Slats by their very nature are there to provide more lift at slow speed. So you could expect slats to be extended whenever the aircraft is in a slow flight regime. Take-off, initial climb out, approach, landing and go-around.

On lightning strikes. I have been struck maybe half a dozen times in twenty years, mostly whilst flying in the UK. In turn most of these strikes were from small innocuous cumulous clouds, and in most cases we were clear of the clouds themselves. Conversely I have been caught in proper equatorial CB's with lightening all around, and survived shaken, stirred but never struck.

So to try to answer your last question. You could be operating your aircraft near an airport, with the slats and flaps extended. And you could easily find yourself being struck by lightning from that small cumulous cloud, without actually being physically in it.

Some years ago there were a series of photographs on PPRuNe showing a B747 climbing out of an Asian airport (I forget which one) and it is quite clearly being struck by lightning!

Lu Zuckerman

To: Capt Chambo

I shall change the storyline to reflect several innocuous Cumulous clouds just above and below the flight path. Lightning can go up as well as down and sideways. Your help is appreciated and it will make the story more believable. The name of the book if it is published is Wings of Wax.

Thanks again. I now have answers to the lightning question and the hydraulics question now; I need to find out what glass panel announces movement of the flaps and slats.

wagtail23

Lu

Have to be careful here as it depends upon which aircraft you are talking about.

The original aircraft were fitted with a 3 station flight deck, ie they carried an engineer. But the later models, and I flew an A300-600, had Electronic Centralised Aircraft Monitoring (ECAM) which consists of 2 screens, one above the other, on the pilots display panel just forward of the throttles.

The top screen shows Engine/Warning Displays (engine primary indications, FLAP/SLAT POSITION, and warning/caution messages)

The lower one is the Systems Display which shows pages, either automatically (which depends on the phase of flight) or by selecting the system you want to see on a push-button panel.

In the scenario you describe having an uncommanded flat/slat movement (which I have never heard of so would like to hear your story) the first thing would be an indication of the flaps/slats movement on the E/WD followed by a message stating that there is a flap/slat fault and there would be an attention getter sound also.

This would trigger the ECAM to show the faulty system on the SD and what actions are required to rectify the fault on the E/WD.

The aircraft has slat/flap brakes which might stop this from occuring, but I am not sure.

As I no longer fly the A300-600 I cannot look into the company manuals to see what the corrective action is or if the shutting off of two hydraulic systems is even recommended. This is because the inadvertant deployment of flaps is a Caution, but a double hydraulic failure (turning off 2 systems) is a lot more serious, depending on the stage of flight, altitude, etc,etc....

Hope that helps.

As far as embedded CBs on approach, you should try to avoid them as there are many documented accidents to prove their effects. During the planning stage, a careful look at the weather forcast should give and indication of what to expect. If there is any mention of fog, CBs etc it is prudent to carry extra fuel for the flight, and hold off until the approach is clear or a diversion is made. That depends upon the flight crew's experience and many other factors which will need more discussion than I can manage this morning.

Like to read the book when complete.

Good luck

wag

ea306

On the A310/A300-600...
Flap Position Indication is displayed on the SFPI
SFPI = Slats/Flaps Position Indicator.
If memory serves me correctly it is located on the forward center instrument panel just right of the engine guages not far from the landing gear selector.

A small detail... but answers one of your questions Lu

Dave

Lu Zuckerman

To: wagtail23

During the developmental testing of the slat system one of the hydraulic modules on the PCU suffered an external leak. They removed the PCU from the test rig and removed the defective module replacing it with another unit. They pressure cycled the new module until it reached 1800 cycles the point at which the original unit failed.

They then reinstalled the PCU into the test rig. The rig was configured for flight mode, which meant that the Command Sensor Unit was in the off position and the computer was turned on. They then applied hydraulic pressure and the slats started to move out at slightly less than half speed. Since the CSU was in the off position the computer was not receiving a command signal and therefore could not respond to the uncommanded movement and the wing tip brake could not turn on stopping the movement. This same basic PCU was also used on the Flap drive system and was subject to the same type of failure.

This problem was never made known to Airbus and was never considered in the writing of the training syllabus and in the Ops manuals.

The problem was traced to an internal leak on the other module (not the one that suffered the external leak), which bypassed the control solenoids in the PCU. The internal and external leaks it was determined were caused by hairline cracks that emanated from a faulty spark erosion manufacturing process. The corrective action in my opinion will only delay the reoccurrence of the problem.

The Flap Slat Computer was never fully analyzed for failure modes and their effects and therefore it was never determined what internal failure or defective system architecture enabled the uncommanded movement.

On the very first revenue flight from Frankfurt to Cairo the flaps could not be retracted during taxi to the terminal. They could not determine the origin of the fault because the “dolls eyes” on the Flap Slat Computer did not indicate a fault. They were forced to return to Frankfurt in a non-revenue status with the flaps extended. At Frankfurt they disconnected the Flap drive and hand cranked the Flaps back to the flight position and reconnected the system. They never did figure out why the computer never detected a fault.

Along the same lines an Air Canada A-320 suffered an uncommanded Flap retraction during takeoff. They were never able to determine what caused the problem. The same manufactures were involved with both programs.

All of this is covered in Wings of Wax. Thank you very much for your input.

Lu Zuckerman

To: All

I want to be as accurate as possible in telling the story so I have another question. In preparation for the landing what verbal instructions would the captain give to the first officer relative to setting the flaps? Also it is my understanding that the slats do not extend at the same time as the flaps. For example at flap setting 1 the slats are not deployed. With flap setting 2 the flaps move further and then the slats start to deploy. Is this the case?

Thanks for the input.

catpinsan

the slat flap settings and sequence for the A310 are as follows:

limit speed / slats/ flaps
245 / 15 / 0 (first position of lever)
210 / 15 / 15 (second " " " )
195 / 20 / 20 (third...)

landing gear down

180 / 30 / 40 (fourth...)

the calls would be of the nature

captain - "speed below 245 - slats 15"
f/o - "checked, selected, moving"
i.e. speed checked,
slat/flap selected by lever,
indication moving on SFPI (see ea306 post)

f/o - when it reaches the position - "slats 15"

as you can see above, first only the slats move (and this is typical for most large jets - the leading edge devices move first)

the SFPI - slat flap position indicator would indicate the movement. uncommanded movement would lead to 2 lights on the overhead panel if an SFCC( S F control computer) fault was detected, and incase of 'assymetry' (and 'uncommanded movement' but i'll have to check on that) the flaps would be locked via "wing tip brakes" and a 3rd light on the SFPI would illuminate. i guess an SFCC fault would register because the flap position would not match that of the lever.

never really heard of this happenning but the only way to stop this would be to pull circuit breakers (locating them among hundreds wouldn't be easy) or to shutoff hydraulics. flaps are powered by green and yellow and slats by green and blue. a dual hydraulic failure (emergency - LASAP - land as soon as possible) is one of the BIG ones on the A310.

if the flaps started moving in cruise for instance at high altitude, it would most certainly lead to a jet upset and be very difficult, if at all, to control. if it happened at slower speeds it could be controllable but would mean flap overspeeds and in an extreme case flap damage or loss. the airbus manual itself asks for overspeeds to be reported only if they are more than 20 kts (if memory serves me right, or atleast 10) or the aircraft is under unusual g loading.

ofcourse hydraulics could be restored after slowing to the appropriate speeds provided the hyds were not damaged due to the flap getting ripped off.

hope that helps

Lu Zuckerman

To: catpinsan

That is exactly what I needed. Airbus document TDD 20 A 001 ELECTRICAL BONDING, LIGHTNING STRIKE PROTECTION, ELECTROSTATIC DISCHARGE states that there are three distinct lightning attach zones on the A-310 airframe. Zone 2 is the airframe, engine, and wing surface behind the engine, the tail surface, and a small area in the outer panel of the wing and a fully extended slat. The fully extended slat creates a sharp protrusion on an otherwise smooth wing leading edge making it susceptible to a lightning attachment.

In order to make the storyline work I assumed a lightning attachment at that point on the slat. The lightning then arcs to a slat jack and then into the fuel tank.

It should be noted that the TDD is very detailed as to how to protect the aircraft from lightning strikes however the second draft of this document was not approved in 1984 and by that time aircraft were in service and on the production line. My interest in getting the TDD approved was because the slats and flaps were not grounded to the airframe and none of the level II contractors would comply with it until the TDD was approved. The fact that the slats and flaps were not grounded and that the flaps could extend with no command sensor unit input is the basis of the story.

I don’t know if WINGS OF WAX will ever be published but in writing it my feelings of rage will be diminished. You cannot believe the problems I encountered in trying to bring these problems to the attention of the level II contractors and eventually to the FAA, DGCA and the CAA and the only thing the FAA did was to get the Vice President and program manager fired from one of the level II contractors but the design was never changed.