Questions tagged [landing-gear]

The wheels of an airplane. Sometimes replaced by floats or skis.

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9
votes
1answer
2k views

What did the “gear warning horn” on the North American P-51 sound like?

I'm working on a sound project for a P51 simulation and I'm having real trouble trying to find a reference on how the P51 gear warning horn sounded like. What mechanisms were used in the '40s to make ...
28
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2answers
4k views

What is the purpose of the Dash 8’s “TOUCHED RUNWAY” warning light?

The DHC-8-400 (and possibly other DHC-8 variants) has (or, at least, had in late 2007, according to Appendix G of this AAR) a warning light labelled “TOUCHED RUNWAY”. The extract of the DHC-8-400’s ...
65
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3answers
21k views

How are brakes cooled on heavy aircraft?

As kinetic energy is not stored or recycled, large quantities of heat have to be evacuated in a short period of time when aircraft abort their takeoff or land: B777 brake test, Youtube Which ...
8
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4answers
1k views

Will landing gear with wheel fairings keep spinning due to airflow?

I asked this in a side note to a previous question, but I figured it warranted its own question. If a fixed gear aircraft is fitted with wheel fairings, even if you tapped the brakes after lift-off, ...
11
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1answer
2k views

What does shimmy in nose landing gear mean?

While I was reading a small article on "Reasons for RTO", I came across a situation where the pilots aborted takeoff because of "landing gear shimmy". What does that mean?
6
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1answer
244 views

Why does the A330 sit nose-down on the ground?

The passenger versions of the A330 have a small but noticeable nose-down angle when sitting on the ground: (Image by contri at Flickr, via russavia at Wikimedia Commons.) In contrast, A330s built as ...
30
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4answers
5k views

Why were flying boats phased out?

Before WWII, flying boats were a popular form of transport, and the advantages are many: No need to build runways, capability of emergency landing on water, availability of large landing sites and no ...
20
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2answers
5k views

Why do aircraft sometimes bounce while landing?

I've seen a few youtube videos where an aircraft bounces once/twice while landing on the runway. Why does this happen?
-1
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1answer
74 views

How is the impact force on the landing gear distributed in fighters?

Upon landing, what percentage of weight is distributed on the main and the nose landing gears of fighters? Upon landing of a fighter aircraft, what would be the approximate time of transfer of the ...
20
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5answers
3k views

Is it better to shut down the engine(s) or leave it (them) running when a gear up landing is imminent?

Is it better to shut down the engine(s) or leave it (them) running when a gear up landing is imminent? I noticed that the pilot in this video chose to shut down his engine before touching down during ...
8
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3answers
538 views

Has there ever been an uncommanded lowering of landing gear?

Has there ever been an uncommanded lowering of the landing gear on a large commercial jet? I could not find any instance of it in a preliminary google search. Could a simple short-circuit cause such a ...
3
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4answers
1k views

Wheel or skid? Which advantages does each one have when used as the landing gear system compared to the other one?

I would like to discuss this topic in depth, as I have not found a clear answer yet. Which are the advantages of using skids instead of wheels (or viceversa) for the following considerations?: -As ...
12
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1answer
7k views

Why do some A320s have double-bogie landing gear?

I believe this is actually a rare sighting, but why do some A320s have double-bogie landing gear? Does Airbus have a specific reason for making such A320s?
1
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1answer
97 views

Exceeding VLO and by how much is too much?

Piper Seminole (PA-44-180) VLO (max gear retraction speed) is 109 KIAS. I've heard that manufacturer published limitations are significantly lower than actual structural and system limitations. What ...
5
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4answers
1k views

What are the advantages and disadvantages of tail wheels that cause modern airplanes to not use them?

Photos' source: Cessna 140 and Cessna 150. According to Wikipedia here, the Cessna 150 is successor of Cessna 140. Both have two-seat capacity and a single engine. Why was the Cessna 150 changed to ...
4
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1answer
278 views

Do landing gear doors need repairs after a gear gravity deploy landing?

I know that landing gears can be deployed even without hydraulic power by letting them go down by gravity, as seen on this video: I was wondering: do the landing ...
6
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1answer
436 views

What is the material of snubber brakes?

What is the material of snubber brakes that is used for stopping the spin of the nose landing gear? KC-135, Boeing 747, 727 are the aircraft that I saw with these snubbers.
5
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2answers
348 views

What main landing gear actuator does the Boeing 777-300ER have?

I can't remember the name of this system was, but all I do know is that is a big actuator that only exists on the Boeing 777-300ER variant. It will pressurize the actuator according to the thrust ...
6
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2answers
279 views

How are the 747-400 rudder pedals and tillers connected to the nose wheel?

The Boeing 747-400 Before Taxi Procedure says (emphasis mine): [...] Flight controls .............................................. Check C [...] Hold the nose wheel tiller during ...
47
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3answers
16k views

Why does the landing gear control have 3 positions (up/down/off) on Boeing 737-800?

I've noticed that Boeing 737-800's cockpit has a 3-position landing gear lever. During takeoff, the pilot moves the lever from DOWN to UP and then to OFF position. What's the point of the OFF position?...
15
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8answers
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What happens to the spinning wheels of the landing gear after takeoff, before retraction?

What happens to the spinning landing gear right after V2 on takeoff? Are they automatically or manually braked to a halt before gear retraction? Or are they allowed to spin to a halt in the wheel ...
3
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1answer
409 views

Why would a Blue Angels pilot leave their gear down?

In a recent Blue Angels airshow, one of the pilots had their landing gear down during the first 5 minutes of the show. What possible reasons would justify leaving the aircraft in this state? No ...
5
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2answers
483 views

Why are landing gear retraction mechanisms mostly based on the four bar system?

I would like to know about the principles of landing gear retraction system and I struggle to find clear information about it. It seems to be about a four bar systems in most cases. This seems more ...
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3answers
6k views

When do pilots deploy landing gear?

The landing gear should be down in order to qualify as a stabilized approach. Other than that, what are the guidelines on when to deploy landing gear on approach?
9
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4answers
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Is there no warning if landing gear is not retracted during flight?

I know that most aircraft have a warning system which makes beeping sounds if an aircraft tries to land without the gear down. After reading this news article about an Air India flight 676 flying ...
20
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5answers
7k views

Why do landing gear tires smoke upon touchdown?

I have been observing several aircraft landings and have noticed that when the aircraft's landing gear touches down, it precipitates the rising of a cloud of smoke. Why is this? (Source: airliners....
4
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1answer
736 views

Why do some helicopters have wheels instead of skids?

I have noticed that Black Hawk helicopters have tires, but I have not seen one take off like a plane. When would a helicopter need to use a running take off or landing? When is it determined ...
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2answers
163 views

For large commercial aircraft, how are the tires changed?

Something at least the size of a 737, all the way up to the A380. How are aircraft tires changed for large commercial aircraft? Are they actually jacked up like with a car?
69
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2answers
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Why are aircraft tires not pre-spun prior to landing to preserve them?

Why has someone not designed a landing wheel with a fin or fins on it so that the air will start the wheels turning before the wheels touch the ground? Wouldn't that preserve the tires longer from ...
0
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1answer
173 views

What indication will appear in case of one of A320 LGCIU is inoperative?

What indication and where it will appear in case of one of LGCIU (landing gear control and interface unit) is inoperative?
11
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1answer
2k views

Why does the A-4 Skyhawk sit nose-up when on ground?

The rear of the plane is nearer to the ground, while the front part of the plane is away from the ground (see image below). Other planes are more flat. I think it was for high AoA but these planes ...
28
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8answers
11k views

Is there a good reason why modern airliners can't have conventional landing gears (vs. tricycle landing gears)?

By "good reason", I mean a reason that we definitely cannot overcome with reasonable changes in aircraft design, control laws or procedures. As possible benefits of this I see a much smaller (= ...
1
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1answer
544 views

Why do we have to do an alternate brake check during preliminary cockpit preparation?

As part of the preliminary cockpit preparation in my company’s older A320s we have to perform an alternate brake system check but not in the newer ones as per FCOM Normal procedures as below. I found ...
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2answers
571 views

What is the purpose of the shuttle valve in a Piper Arrow's landing gear system?

This is the PA-28R-201 landing gear hydraulic system diagram. I am wondering how this shuttle valve functions. Research I have done indicates that a shuttle valve blocks one attachment to the valve ...
0
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1answer
121 views

How does landing gear affect thrust on a light twin-engine airplane?

I'm working on my commercial multiengine rating. And I got this question from my examiner, and I answered: landing gear produces penalty drag, so it decreases thrust. But the examiner says this isn'...
40
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3answers
2k views

Why is the Eurofighter's nose gear door shorter than the bay?

The Eurofighter Typhoon has an interesting "feature" in that the nose gear door is shorter than the nose gear bay itself by a good few inches, as shown here: Can anyone shed any light on the reason ...
16
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4answers
4k views

How do landing gear retracting into the wing affect performance when deployed?

On many aircraft with low wing, landing gear (either wheel, leg, or both) retracts into the wing. Thus, when deployed, a significant part of the lower surface of the wing is not as clean as when the ...
3
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2answers
193 views

Why does only one hydraulic intake line from the reservoir have a filter on the Arrow II?

This is a portion of an Arrow II landing gear hydraulic system diagram. I noticed that there are two intake check valves, one located on each side of the pump, that would allow flow from the ...
2
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0answers
159 views

What is the difference between a pressure switch, high-pressure control, and low-pressure control in a landing gear hydraulic system?

This is an Arrow II landing gear diagram. In the diagram, the high and low pressure controls look like check valves. The pressure switch is unclear. What are these three items, and what purpose ...
6
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1answer
754 views

What is the maximum weight on the main gear of a large aircraft at rotation and touchdown?

For a large aircraft like a B747 or A380, how much does the weight on the main gear increase when the nose gear is in the air? I mean, in these two cases: What is the maximum extra weight on the main ...
1
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2answers
605 views

How much more economical are planes with retractable gears vs. those with fixed gears?

Many small planes have fixed gears, some have retractable gears. All things being equal, the plane with retractable gears would have to be more expensive than fixed gears, as the mechanisms involved ...
12
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3answers
3k views

Does Nitrogen inside commercial airliner wheels prevent blowouts on touchdown?

I just watched the first episode of Inside Mighty Machine where civil engineer-turned-host, Chad Zdenek, discussed innovations of the 747. One innovation he discussed was the increased number of ...
3
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1answer
474 views

How can the landing gear of an A320 be lowered in the event of a simultaneous hydraulic and electrical failure?

What is the process for lowering the landing gear of an A320 when the hydraulic and electrical systems are not operational? What happens to the aircraft when you lower the landing gear with ...
9
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5answers
2k views

Has there ever been a tail-dragger with retractable tail-gear?

This comes from a slightly related question about drag from landing gear. A tail-dragger is the old-school layout of aircraft, particularly WW2-era fighters. It's also known as Conventional Landing ...
3
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2answers
2k views

Why complex landing gears are used instead of simple, reliable and light weight muscle wire or shape memory alloys?

Muscle wires actuators are really simple, have a high power density and are reliable. Landing gears on other hand are used only twice per flight while taking off and landing (if everything goes well ...
6
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3answers
1k views

Nose gear failure in single prop aircraft: belly landing or nose landing?

Let's say we are flying a single prop airplane with tricycle format retractable gear, such as a Mooney Bravo or a Piper Comache. The nose gear fails mid-flight and is unable to be lowered. Is it safer ...
9
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3answers
3k views

Why is the Constellation's nose gear so long?

The Lockheed Constellation has an enormously long nose gear, which causes the aircraft to slant appreciably backwards when sitting on the ground: L-049 (Image by Greg and Cindy at Flickr, modified ...
5
votes
1answer
346 views

Does the PA-44's squat switch disable the stall warning?

I've read the AFM and looked online about the gear system for the PA-44 Seminole and there is apparently a squat switch on the right main gear that disables the stall warning whilst on the ground. ...
38
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4answers
7k views

Do commercial aeroplanes use ABS to brake?

I have read that the wheel brakes on an aeroplane are by for the most efficient means of stopping it. I was wondering whether in low grip situations, such as in rain or snow, an ABS (Anti-lock Braking ...
19
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3answers
7k views

How are modern jets modified to takeoff/land on a dirt runway?

I've been reading a lot about the Soviet and Russian military aircraft, and it seems a lot of them are built to work on dirt runways, or modified to do so. How is this accomplished? Is it a simple ...