PA 28R nosegear doors

[pilotbear]

A couple of days ago I was flying a PA28R 200 mk1.
During a descent from FL 60 at 500'/min, 120-130kts TAS, 18" MP 2400rpm there was a bang and a lot of noise and vibration from the front end. The gear in transit light also came on.This occurred at 4000'.
After about 30 seconds in which I was deciding whether I was going to land in the nearest field and get the Eurostar home, the noise stopped and everthing was normal.
After a tower insepection of the gear I landed OK.
On the ground I discovered half of the nosegear door missing on the starboard side

It has been implied that it was my fault because; :*

a) I must have exceeded Vne, well this is almost impossible without a 60deg bank nose to the ground and full power, I am sure I would have noticed - besides I was doing a cross channel check on someone and I think they would have noticed too.
or
b) I put the gear down at too high speed, well I did not. I have a lot of time on complex a/c and I am quite pedantic about speeds especially when I am teaching.

both of which are b:mad:ks

c) a birdstrike, except there was no debris.

Has anyone of you experts got an idea of what might have caused this?:confused:
Often the gear in transit light comes on in a tight turn or when levelling off from a descent. I mentioned this a lot but am told by the owner it is normal.

The other question is please does anyone have a source for this part as now the a/c is grounded.

thanks:ok:

[Genghis the Engineer]

I don't know the variant specifically, but if I were you I'd ask a competent metalurgist to take a look at the retained half of the broken bits and look for evidence of metal fatigue which is the most likely reason for something to fall off an aircraft within the envelope.

G

[pilotbear]

Actually the door is made of fibreglass, I guess there may have been a weak point on it. But the gear was not selected down at the time.:confused:

[Genghis the Engineer]

Well I was clearly telling the truth when I said I didn't know the type:}

However, there is such a thing as composite fatigue, a good LAME qualified in composites will be able to examine it for that (up to a point, it's very hard to spot).

Or was it the hinge that went?, I'll bet that wasn't fibreglass !

G

[pilotbear]

Here is the funny thing. It ripped half the door off the hinges. The hinge is still there with the rivets remaining.:eek:

I am more concerned with why the door got itself in a position for this to happen considering the speed wasn't excessive and as I said the gear was selected up. :hmm:

[Genghis the Engineer]

Composite fatigue works by microcracks building up within the matrix (that is the bit that isn't fibre) and weakening the overall material - it could be the culprit and just the result of years of loading.

Or of-course it could be something else!

G

[SeldomFixit]

Nothing will cause a door to fail more quickly than being rigged too tightly closed. Every gear cycle sets up stresses around the actuator rod end attachment. Ultimately, the mount is torn from the parent material. This may have been a factor in your instance. Do you remember from your walkaround whether or not the door appeared to be underflush ? Did it appear to be sitting proud perhaps ? In this case, it's not impossible that repetitive exposures to slipstream could have played a part in weakening the structure. As Ghengis has said, composite stress is VERY difficult to detect until such times as you have a failure.
I have seen instances of gear strut doors, also wheel well doors on widebodies fail because of being rigged too firmly closed.
Like Ghengis, I'm not familiar with the type but am surprised that you would have composite doors.

[pilotbear]

Thank you. That is quite an interesting theory. I don't remember anything unusual. But, in hindsight I will make a closer inspection of these things.:ok:

[HiSpeedTape]

Errm... the only way to tell if the nosegear doors are correctly rigged on a Pa28R is to jack it and do a retraction as the nose bay doors are open with the gear down ie on the ground. Therefore, the chances of being able to spot anything amiss during a normal preflight would be slight unless you were looking specifically for signs of fatigue around the gear door actuator (rods) mountings (. One thing to watch for is that the rectraction rods have been fitted in the correct position in relation to the Y shaped retraction/drag brace. They are not murphy proof!
Hope this helps though as you have explained that the door departed company with the hinges, it would be equally likely that the doors may have been misrigged and not faired correctly. causing aerodynamic forces to impart loads into the retraction/drag brace to which they are attached. This brace also forms the overcentre downlock function for the nosegear.

HST

[Genghis the Engineer]

One or two idle thoughts...

Composite fatigue. This is poorly understood, even by people who look for it for a living - this isn't to criticise them, just that the Human Race as a whole hasn't really come to grips with it yet. Similarly the basic strength of composite parts, when new, varies far more than metal ones.

For that reason, we apply huge safety factors to composite structure when it's approved. This should mean that when it's brand new you'd have to overspeed by (rough back of envelope sum) 50% to damage a composite component in the airflow, and if Piper got their sums right (which is by no means certain for the reasons stated above and not because I've anything against Piper) by at-least 18% to damage the door at any point in the predicted life of the aircraft.

Problem with the microcracking in composite structure that constitutes fatigue is that the only way really to spot it is to cut the structure open in a lab - which is rather pointless since you then can't fly it again anyway. The way it actually affects the structure is to make the whole thing weaker - a very different effect to metal fatigue which introduces small numbers of (reasonably) detectable cracks that simply create identifiable - particularly after a failure.

If you are really in trouble, rather than just being grumbled about call AAIB on 01225-510300, they'll almost certainly have some suitably qualified materials experts on their books that they can point you at. But, be warned that anybody good enough to do consultancy for AAIB is not going to be cheap.

On the other hand, one hopes that this was (okay it's borderline on whether it's a reportable accident or not but good practice says you report it anyway) reported to AAIB and they may look into this in ther own light and budget. It may be that they'll find something akin to what HiST suggests, and might want to make recommendations to Piper that would make everybody's life easier!

G

[Nopax,thanx]

You could try F & H for a replacement door....

01778 342826

...and no, I don't work for them!!!:p

[pilotbear]

Thanks a lot guys. I am not 'in trouble' over it so to to speak, however the boss likes to think the pilot is at fault and never the a/c. The over tightly rigged idea seems quite feasable.

Actually, I have a friend associated with the AAIB and he is making enquires for me.

cheers

:) :ok:

[lunkenheimer]

Okay, I'm not an engineer (on aircraft, anyway) but doesn't the 'gear in transit' indication reported by Pilotbear seem strange? Could the gear have a fault in such a way that it shifts during high-g manoeuvers and pushes on the door, causing excessive loads?

Seems surprising to me to regard a gear-in-transit indication as normal at any time except when the gear is expected to be in transit :confused: