What Happens If A Plane Lowers Its Gear At Cruising Altitude?

Particularly when sitting towards the center of an airliner, the noise of an aircraft’s landing gear being lowered is fairly conspicuous. These wheels are typically deployed shortly before a flight lands, and, for keen-eared passengers, they are a surefire sign that touchdown is imminent. However, briefly delving into the realms of the hypothetical, why don’t we have a look at what might happen if a plane’s gear was to be lowered during its cruise.

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[space_]

34, 000 ft in 1 minute - what a ride that must have been for the pilots

[davidhynd]

"Losing 34, 000 feet of altitude in a little over a minute" - After landing passengers were issued with a heartfelt apology. And clean underwear.

[sammcgregor]

Ok, I’ll tell a tale of gear lowering at 36, 000 feet! I was telling my thoroughly disinterested First Officers some anecdote which involved landing gear and reached out and touched the landing gear lever very lightly, but not knowing that there was a fault in the electrical unit it was attached to, and the gear doors promptly opened. The nose dear bay being right beneath the flight deck this was very loud and the poor FO believed momentarily that we were having an explosive decompression! Fortunately the IAS was indeed below the limiting speed for landing gear extension, but having some distance to go on the flight something needed to be done and the best I could come up with was to slow to landing gear retraction limiting speed, lower the gear, then retract it and hope the doors closed. The reaction of the autopilot was interesting to say the least with some pitch changes that you don’t see with landing gear extension at normal altitudes, but it maintained the level and the doors closed after retraction so we proceeded to the destination keeping my hands well away from the lever until I meant it! It was also one of the more interesting PAs I’ve ever made to passengers…

[paulstreeter]

I was a Captain of an A320 en-route from LHR to GIB some years ago.
During the climb at approx FL200 300Kt we had a main gear brake unit overheat warning
The ECAM instructions were to lower the gear which was accomplished and then I diverted to LGW.
Subsequent investigation showed that I had grossly exceeded the max speed for gear extension. No mention of this IAS speed restriction was made on ECAM.
Nevertheless, this is one of the standard aircraft limitations which pilots are expected to memorise and I was left in no doubt as to my own shortcoming !
Incidentally the aircraft G-TTOC suffered no damage and returned to service immediately .

[mapleleafaviation]

Heard of that situation in one scenario I can name, during the events of Korean Air Flight 007 they plane lowered its landing gear during cruise to stop the plane climbing after an explosive decompression caused by a missile launched by a Soviet fighter.
It did help the plane slow down but sadly crashed into the Pacific Ocean, that’s one good example I know. But awesome video!

[aerobobby]

I’m a Landing Gear Systems Engineer. Uncommander gear extension during cruise is classed as catastrophic. This is because you have to assume that the failure that caused the gear to extend also means you cannot retract it again. On some ETOPS routes, the fuel burn is so significant with the gear down you would have to ditch at sea… which is catastrophic.

[chriskerker]

Most jets have an airspeed and a Mach limit for extending and retracting the gear. Doesn’t matter what cruising altitude you’re at as long as you’re below that Mach number.

[Roland_Rohrle]

A mate of mine flies 737’s for VA. I can’t remember the exact details, but they had to fly Melbourne to Sydney with the gear extended with a full load of passengers. He said the noise and fuel burn was crazy! Plus the lower speed meant they arrived before curfew with 1 minute to spare…

[getdachoppa]

Along the same vein of the topic, in 2017, the crew of an Air India A320 never raised the gear after take off. The extra drag caused them to divert & make a precautionary low fuel landing.

[pilotmaxim]

This summer i was heading to Frankfurt on a Lufthansa A320 enroute from Budapest when the pilot came on the PA at cruising altitude saying that warning lights and warnings came on and that the landing gear needing to be lowered for a minute was baisicly the only option.
The aircraft slowed down and put out the gear for about 1 minute wich produced higher noise levels but was nothing much that bad.
We landed safley at Frankfurt 1 hour later

[noonedude]

I put the landing gear down when I had a severe elevator control malfunction as the PIC of a Cessna 421 just off the coast of Florida. It greatly assisted in getting the nose down, preventing a stall and eventually allowing for a very abnormal but all in all safe landing at the diversion airport.

I recall it being one of my smoothest landings ever, but I was so juiced on adrenaline that maybe I was just happy to feel pavement again 😅

[stephen_]

On the 747-400 you can lower the gear at 240 knots and use it as an additional speed brake. And boy does it work - very loud though.

[markiangooley]

On some CRJ models, any passenger hears quite a noise when the landing gear is lowered. Disconcerting until one gets used to it.

[USAFA]

Many modern airliners, the 737 being the one exception I know of, have what’s called a BTMS (Brake Temperature Monitoring System). In the case of a high brake temperature, sometimes up at cruise, the QRH checklist will instruct the pilots to lower the gear into the airstream to make sure if there truly is a hot brake, the cold atmospheric conditions can help cool them down before they are retracted again. When this happens the pilots simply slow the aircraft to less than the maximum landing gear extension speed and drop the gear. As stated in the video, up at altitude, the aircrafts indicated airspeed is probably already below the maximum gear extension speed. The next issue is that on some aircraft, the maximum gear retraction speed is lower than the gear extension speed so the pilots would need to take that into account prior to raising the gear once the brake temperatures have cooled sufficiently. Hope that helps provide another scenario in which the gear would intentionally be lowered in cruise.

[jammymcjammerson]

When I was on Kc-135s, we dropped the gear for steep descents all the time. No pax means no dealing with their "comfort" bs. Plus the speed limit for the gear was the same for t he plane's clean configuration, although the doors could only handle like 250kias/0.85m or something like that but that's still p fast especially at fl300+

[letsseeif]

At the cost of losing landing gear doors, lowering the wheels is a real and effective 'last ditch' strategy. In a similar situation, I'd use this to literally steady the ship/plane. It'd be a backup to lower IAS airspeed enabling some spoiler deployment while pilots concentrated on the 'A''s - airspeed, attitude, altitude, (& other dynamics) giving essential time to set things right in context.

[AidenTheAviator]

In 1985, China Airlines flight 006 entered a steep spiral dive from 41, 000 feet after one of the 747SP’s engines failed and crew failed to compensate for the imbalance in engine thrust. The aerodynamic forces of the dive tore the main landing gear doors off and forced the gear down into a locked position. The pilots were able to level out at 10, 000 feet but were unable to retract the gear due to damaged hydraulics. The increased drag meant they couldn’t continue to their destination of LAX so they had to divert to San Francisco.

[HoLTeam]

I looked up that TWA in 1979. Piloted by "Hoot" Gibson, who turns out to NOT be the 5-time Space Shuttle astronaut. Notably, the astronaut "Hoot" Gibson went on to fly commercially after retiring from the astronaut corps in the 90s. Strange coincidence with the names, careers, and nicknames.

[groundstar]

Hapag-Lloyd Flight 3378 (HF-3378) from Chania, Crete, Greece, to Hannover, Germany. On 12.07.2000, the aircraft flying the route, an Airbus A310-304, registration D-AHLB, with passengers and crew on board, set off for Hannover leaving the landing gear fully extended, as a precaution, since a malfunction had prevented its proper retraction after take-off. The plane eventually ran out of fuel while attempting a diversion to Vienna, crash-landing just short of runway 34. No fatalities resulted, although the aircraft was written off.

[A.hdh.]

I love the 757 content at the beginning of the video