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This morning, I took flight VS156 from LAS to LHR, aboard a 787, tail number G-VSPY according to flightradar24. The pilot made a strange announcement before takeoff - specifically, that due to a recent maintenance procedure, the pilots would not be able to raise the gear for the first 10 minutes of flight. The rest of the flight continued normally. What was the procedure likely to be, and why would leaving the gear down be safer?

catalogue_number
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  • I have not heard of that situation occurring for maintenance reasons, but I know that it is done occasionally when the brakes are too warm due to a previous flight being on the heavier side and a really quick turnaround time. Leaving the gear down in that situation would be giving it the cooling that it did not get at the gate. – SMS von der Tann Mar 13 '23 at 23:26
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    That would be quite surprising here, considering that the turnaround was around four hours (and the weather was fairly cool)? – catalogue_number Mar 13 '23 at 23:35
  • @MikeSowsun Nice find - I suspect this answer to that question is most likely to be the case here. Or 757toga's answer below. – Ralph J Mar 14 '23 at 00:03
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    @RalphJ If the gear cannot be retracted after takeoff because of a gear/brake issue (re: required quick turn around limitation, excessive brake temp indication on the EICAS or similar, known wheel brake issue, etc.) then a departure should not occur until the issue is resolved. Or, compliance with an MEL requirement like shown on the MMEL in the answer below. Meeting the takeoff performance climb gradient needs to be considered in the event of an engine failure. –  Mar 14 '23 at 00:46
  • @757toga What's suggested in the other answer I linked to would be an MEL for a particular wheel's brake, with a proviso for time with the gear extended to allow the wheel to spin down (without the normal braking) before retracting it. The other answers to that question seemed unlikely to me too, because they do seem to beg the question of getting maintenance done before flight. I don't know if an MEL such as that answer posits does exist for the 787; the reference you provided makes the fire detect MEL a likely scenario. Either way, engine-out + gear-down climb data would clearly be needed. – Ralph J Mar 14 '23 at 02:57
  • @RalphJ I agree. –  Mar 14 '23 at 03:03
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    What's weird to me is why would they tell you about this? I'm sure random stuff like that happens all the time, but the passengers really don't have any need to know about it, and telling them can only lead to confusion or possibly even panic, which is the last thing you want. – Darrel Hoffman Mar 14 '23 at 13:55
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    This was to reassure us that any additional noise/buffeting in the cabin was normal. – catalogue_number Mar 14 '23 at 15:41

1 Answers1

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It could be that the Wheel Well Fire Detection System was inoperative.

According to the B-787 "Master Minimum Equipment List" (as shown from this website, in pertinent part) the Wheel Well Fire Detection System:

"May be inoperative provided landing gear remain extended for ten minutes after takeoff."

enter image description here

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    This is the most probable reason for leaving the gear down for 10 minutes. – Mike Sowsun Mar 14 '23 at 00:55
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    Yeah that was it. "Maintenance procedure". Imagine the freakout if the pax knew you were able to depart with all sorts of systems not working lol. – John K Mar 14 '23 at 01:49
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    What is the idea of keeping the wheels out for 10 minutes? cooling them down so they won't catch fire? – fraxinus Mar 14 '23 at 08:42
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    @fraxinus If the wheel is on fire, (for example, because a brake did not release) you do not want to retract the wheels, because that mean you are putting fire into an closed box near hydraulic lines – Ferrybig Mar 14 '23 at 09:10
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    The fun part for the pax is when the pilot retracts the gear immediate in spite of the first announcement. After the engine becomes mysteriously exceptionally loud, or exceptionally silent. – Klaws Mar 14 '23 at 10:15
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    That use of "provided" is very curious. https://www.merriam-webster.com/dictionary/provided "on condition that : with the understanding : IF". – RonJohn Mar 14 '23 at 17:25
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    @RonJohn It's standard verbiage for MELs. A "proviso" = "provided." –  Mar 14 '23 at 17:31
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    @RonJohn The curious part to me is the wording "may", since I initially read it as "may become inoperative if..." which was like...why would you want that?? (Vs. upon re-reading, it is "allowed to be inoperative if"...) – user3067860 Mar 14 '23 at 18:56
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    This question may end up being closed as a duplicate; since this is by far a better answer that the speculation answering that question, please consider posting this as an answer there as well so that it's easily findable for anybody who reaches that thread with a similar question. – Ralph J Mar 14 '23 at 21:32
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    @RalphJ I thought about that, but I don't know that the A333 has a wheel well fire detection system (I looked thru the A320 MMEL and could not find one). The OP asking the other question (maybe duplicate) specifically refers (in a comment) to a B788 (B787) and a A333. Also, it is the specific mention of 10 minutes in the B787 MMEL that seems to differentiate between the two questions. I'll take another look tomorrow. Thanks –  Mar 14 '23 at 23:22
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    @Ferrybig The issue isn't the wheels on fire, the issue is if there's leaking hydraulic fluid in the wheel well, the hot wheels and brakes can ignite it. Leaving the wheels out allows hot surfaces to cool below the ignition point of hydraulic fluid. – user71659 Mar 15 '23 at 03:00
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    @RalphJ: old questions can get closed as duplicates of newer ones that have definitive / canonical answers. The duplicate system exists to organize and link questions, and it works fine to use it even when a question wasn't a duplicate at the time. (Of course, if there are other good answers on the older question, then it should be the canonical Q&A that others point at, and yeah then it makes sense to repost an answer. And in this case, this question has more details, and a difference in that the announcement gave a time.) – Peter Cordes Mar 16 '23 at 07:59
  • @user71659 I think it's common in technical writing for "May" to always refer to permission, rather than uncertainty. (RFCs, for example, always have a section explicitly defining terms like "may", "should", "must", etc.) – chepner Mar 16 '23 at 13:24