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Retracting Landing Gear on Ground

VCSEL

New member
Hi, my first post here, coming from watching the 74 Gear channel which I enjoy very very much. I think that I might have a little information to contribute.

In the youtube video about video memes it was said in conjunction with the "when Homer Simpson returns after quarantine" part that the landing gear can't be accidentally retracted when the plane is on the ground. There is also a reference to the Hollywood vs. reality video about "Con Air" where the pilot appears to have selectively retracted just the nose wheel to retard the plane in a Gimli Glider style.

However, in 1990 a Crossair Saab 340A was destroyed when an instructor wanted to demonstrate that the landing gear could not be retracted on the ground but it actually did so.
Sources:
https://en.wikipedia.org/wiki/Saab_340#Hull_losses
https://en.wikipedia.org/wiki/Crossair_Flight_3597 (section "Final Report")

Maybe the Saab 340A stands out by not having a safety mechanism like the one that was briefly mentioned in the Con Air video... I have no clue.
 

Siris

Active member
Hello and welcome to the forum!

Aircraft have a fault switch on the gear that is open when the gear is compressed to prevent accidental retraction of the landing gear. Like anything mechanical this can fail and so shouldn't be relied upon entirely to prevent the gear from coming up early.
 

MsHighAltitude

Active member
Hello and welcome to the forum.

I've heard when the aircraft is parked, there's some kind of pin that's put in place to secure the nose gear and avoid situations like this:
1621225175618.png

When the plane is taxiing to the runway, the ground crew wave to show that the nose gear pin is out. In Japan they bow as well... gosh I miss that place.
 

321Captain

Member
Gear pins on airliners are usually only installed when maintenance is being performed on it. They will put the pins in when they are towing the plane to the hangar etc. The pin that you see the ground crew wave, or bow in Japan about is the steering bypass pin. When you push back, the tug driver puts a lever in bypass, removing hydraulics from the nose wheel steering so that they can turn the airplane. That pin holds the lever in place. When the pushback is complete, they remove the pin and show you that they have it. This lets you know that you will be able to steer the plane on the ground with the tiller. There have been times in my career where I had to call maintenance to come out to our plane after the crew left the pin in. We couldn’t taxi out, no nose wheel steering.😜
 

Siris

Active member
Gear pins on airliners are usually only installed when maintenance is being performed on it. They will put the pins in when they are towing the plane to the hangar etc. The pin that you see the ground crew wave, or bow in Japan about is the steering bypass pin. When you push back, the tug driver puts a lever in bypass, removing hydraulics from the nose wheel steering so that they can turn the airplane. That pin holds the lever in place. When the pushback is complete, they remove the pin and show you that they have it. This lets you know that you will be able to steer the plane on the ground with the tiller. There have been times in my career where I had to call maintenance to come out to our plane after the crew left the pin in. We couldn’t taxi out, no nose wheel steering.😜
Yeah I can imagine with that much weight and momentum "free castering" isn't really a thing. :p
 

MsHighAltitude

Active member
Gear pins on airliners are usually only installed when maintenance is being performed on it. They will put the pins in when they are towing the plane to the hangar etc. The pin that you see the ground crew wave, or bow in Japan about is the steering bypass pin. When you push back, the tug driver puts a lever in bypass, removing hydraulics from the nose wheel steering so that they can turn the airplane. That pin holds the lever in place. When the pushback is complete, they remove the pin and show you that they have it. This lets you know that you will be able to steer the plane on the ground with the tiller. There have been times in my career where I had to call maintenance to come out to our plane after the crew left the pin in. We couldn’t taxi out, no nose wheel steering.😜
Thanks for the clarification captain!
 

Brongaar

New member
On the F/A-18, have a proximity switch, that when weight on wheels, the switch is 'on', telling the aircraft that it's on the ground, when a special pin is inserted, turning the proximity switch in the 'off'position, in the main gear, that is where the avionics are tested on an 'O' level.
 

Roichi

Active member
We do have gear locking pins on our company aircraft. They are used when the aircraft is parked to secure the landing gear in position. Because switches can fail and stuff can happen. These pins have flags on them and are stored in the door. So the crew takes them out themselves after parking.
We fly mostly Bombardier planes.
 

321Captain

Member
Sure. All airlines will have different policies concerning gear pins. All it takes is for a flag to be missing or a not perfect pre-flight inspection, and guess who is coming back to the departure airport for an unscheduled arrival. The size of the airline and the number of instances like the one I described are the primary driver of gear pin policy. It is also driven by the aircraft type(s) flown. Most airliners have pretty solid ground/air logic and or overcenter locking mechanisms to prevent ending belly up on the ramp. 😬
 

Drew748

New member
I'm an Ex-Line Mech (still miss the industry), installing the gear pins and gust locks was a daily job on all our fleet once the nights flying was completed (Freight Dogs - DHL Feeder Flights - Mail Flights)... Pins and Locks all have "REMOVE BEFORE FLIGHT" flags, and a Tech Log entry made on installation and removal to ensure the crew are informed.
 
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