Return to Service experience

[gums]

Trying to get off the main Pprune discussion about the 737 and the clueless folks there.

I have gone thru two stand down episodes in my lite experience. We didn't put the planes in the desert, but we ran the motors and exercised the hydrualics and flight controls best we could every few days. When the planes were released to fly, they had a qualified FCF pilot run around the circuit and then we basic toads flew them.

I would be interested in those here that have gone thru such, and I fully appreciate that this 737 stand down is likely the longest one on record, best I can determine.

[FlightDetent]

In the civilian world, mothballing for 2 or 3 years would not raise an eyebrow for the uniqueness of it. One could expect some logistical challenges when reviving such a large fleet at once; darn the pandemic took care of that. :(

[FullWings]

We have been bringing aircraft in and out of service, some of them having been parked up for a month or two but with regular engineering input. We haven’t had any pitot/static issues but a *lot* of pack issues, including several double failures in flight. As a pilot, I just note from the AML that it hasn’t flown for xx days and raise an eyebrow to a corresponding level...

[gums]

Yeah, I guess the civilian fleets do not require as high a percent of "full mission capable" planes, but still a healthy number.
Our biggest problem was with hydraulics due to seals hardening up, actuators leaking, or valves "sticking".
I was also wondering if there were special procedures for first flight, as I noted for our military episodes.

[tdracer]

Gums, there are very specific AMM procedures for aircraft storage - somewhat tailored for the expected length of storage - although I'm not familiar with the specifics. Aircraft go out off and back into service on a somewhat regular basis (Boeing sometimes does 'build ahead' - operators generally want to take delivery right before the summer peak season, but monthly production stays consistent - so aircraft go through production flight test then right into storage for several months prior to delivery), although not often on the scale we're currently experiencing. I think the only previous large scale experience was after 9/11 (in early 2002, United was taking delivery of new 777s (sans interiors) and flying them to the desert and parking them). This one is also unique that an entire model of aircraft has been affected for an extended time.
As for a check flight - again I'm not familiar with the specifics - but I'd expect that the positioning flight from the storage location to the return to service location would be used as the check flight (which is when the subject IFSD occurred).

[DaveReidUK]

It's no coincidence that in the past, aircraft temporarily taken out of service have tended where possible to be stored in warm, dry, low-humidity locations.

For obvious reasons that hasn't necessarily been the case for the large number of grounded Max aircraft. The indefinite length of the grounding won't have helped with return-to-service planning, either.

I'll be surprised if there isn't an above average incidence of RTS niggles.

[Dave Therhino]

Paragraph (m) of AD 2020-24-02 (the AD that requires the 737 Max flight control system changes) requires an "operational readiness flight" to be performed after the required modification work has been performed.