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Post-maintenance check ?

I have never heard of any checklist including that sort of items. Airlines do not have them AFAIK. Of course I suppose you could have a list of items to cover during pre-takeoff briefings, pre-approach briefings etc.

A post maintenance checklist would probably be a good idea. You would probably tailor it to the kind of maintenance that has taken place.

LFPT, LFPN

Peter wrote:

One Greek TB20 pilot would have a “story” to tell after a major avionics upgrade in a top firm in Germany, and that wasn’t an avionics config…

Ohh yes.
My biggest “Post-maintenance check” lesson learned.
A very reputable European avionics shop does a good work I had flown the TB20 there for.
I pick the TB20 up with a scheduled IFR flight back home having to pierce through a solid IMC low cloud (VMC on top, above valley, warm temperatures) situation.
Off I go in to the SID, after few seconds of climbing I engage the autopilot on an ~1000 ft./min climb on VSI mode and Altitude preselect once I establish climb speed.
In few seconds while in IMC I see airspeed dropping wild.
Power (MP & RPM) are where they should be BUT the VSI is at 200~300ft./min (instead of 1000~1100 at this pitch & power), Altimeter not climbing as it always does and PITCH rising rapidly.
Stick n’ rudder instinct makes me disconnect A/P and pitch down immediately, without second thought.
It was the fundamental though that PITCH maintains my speed and anything else comes after this.

I duck down below the few hundred feed of overcast I had just entered, (no terrain below, just a valley), speed picks up as expected and once visual I cancel IFR and return for landing.

Avionics people were already at the ramp when I taxied in worried.

We open up the cowl and find what I suspected.

The pitot-static tube feeding the altimeters was bent when they put the hinged panel back in to position.
This blockage resulted in minimal change of the altimeters when climbing, VSI mode feeling it was not climbing and hence the autopilot pitched up to capture the VSI I had entered.

Lethal trap caught in split second’s instrument scan and the “gut feeling” that something was wrong.

It is a known weak point of TB20’s and they and I should have checked for it.

They fixed it with a strengthened tube fix, they did not apologize, I was pissed, they even dared to charge me for the labor, I denied to pay, we said goodbye, refiled IFR and off I went back home.

What pissed me off was that I trusted “all should be well” and I did not do a local VFR flight to check all was well before jumping in to known IMC in an IFR flight.
What pissed me off was that it had happened to me before back home after an annual, I had discovered it on the very post maintenance flight exactly for this reason (to check if all is well) and still I had not learned my lesson. Well this time I learned it.

I also learned the lesson that, especially in IMC, I should first stabilize the aircraft in what I expect it to do by flying manually, gain some altitude then engage Flight Director, check again, and THEN engage the autopilot.

TRUST BUT VERIFY is the key phrase and that includes a post maintenance VFR local flight.

Last Edited by petakas at 31 May 21:01
LGMG Megara, Greece

That is one good story. And very scary. And a very good argument in favour of not flying in IMC after maintenance.

Reminds me of the airliner that had all static ports blocked by duct tape at night. It did not end as well.

Last Edited by Aviathor at 31 May 21:07
LFPT, LFPN

I have an even better one …
A guy I know picked up his Citation Jet at (another) avionics firm after a major upgrade. When he switched on the A/P in 1000 feet the airplane started a roll and only stopped when he disconnected. One of the computer connectors to the autopilot had fallen off because it was plugged … but not secured with the screws.

I wonder how they did not catch that during the pre-flight control checks.

LFPT, LFPN

IIRC, the indication on the PFD was still correct, you would have had to look at the ailerons, and they are not visible from the cockpit unless you open the window and lean out maybe.

Rwy20 wrote:

the indication on the PFD was still correct

That would be a problem that should be addressed. However, the article states

Clues might have been seen on the ECAM screen during the flight control checks, but often pilots only check for a deflection indication, not the direction. Before the aircraft left the hangar a flight control check was performed by the mechanic, but only using the first officer’s sidestick.

Controls free and correct

LFPT, LFPN

Mike Busch has just done an article in the US AOPA mag about post maintenance checks…

Here are some points:

  • Assume the maintenance activity was NOT followed by anybody checking anything
  • Check external fasteners
  • Check flight controls
  • Check all switches and other electrical controls – they may be in useless settings
  • Make sure oil pressure comes up quickly after starting
  • Check taxiing works ok, with proper control
  • Do a run-up and check brakes are working properly (not spongy)
  • First flight must be in VFR conditions, no passengers except the mechanic(s)!!
  • Keep near the airport for a while, in glide range
  • Check all avionics work, and cockpit and instrument lights
  • Don’t collect the plane on a Friday (several reasons, one of which is the work may have been rushed)
  • Make sure you have the signed paperwork with you when you fly

Interesting stuff to hear from a “mechanic” and I can say I have seen must of the above issues myself at various times in the past, collecting the plane from a company.

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Shoreham EGKA, United Kingdom
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