Cessna Main Whell Snap?
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Joined: Feb 2005
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From: Vancouver
Cessna Main Whell Snap?
Just wondering how strong the main gears are on a single piston engine Cessna. I have heard some people actually can break these on a landing? Like during a ground loop (how does a ground loop happen?) or a stall from flaring too high (how high of a fall can the gear endure?)
Any sites where I can see photos or videos of bad landing resulted in main gear snapping off?
Any sites where I can see photos or videos of bad landing resulted in main gear snapping off?
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Joined: Feb 2000
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From: UK
Pretty much all light aircraft undercarriages are designed and built to the same structural requirements, and thus all are equally unlikely to fail.
How to break an undercarriage?
(1) Flare much too early, and stall in. Some professional knowledge added to a quick back of envelope sum tells me that to break a Cessna undercarriage you'd need a closure rate with the ground of at-least 10 ft/sec and probably nearer 14 ft/sec. That equates to a straight drop, with no lift acting at-all (which wouldn't be the case) .
(2) Land on a totally inappropriate surface, for example drift off the runway centreline and stick a mainwheel down a large rabbit hole. This does happen, but is not the undercarriage's fault.
A groundloop occurs when the pilot loses directional control of the aeroplane on the ground - this is almost impossible to achieve in a nosewheel aircraft and is largely a taildragger problem. When it does occur, a properly designed undercarriage should take it without any problems.
So, handle the aircraft as intended, and put it down on a runway surface each time, you can probably go your entire life without seeing an undercarriage failure.
G
How to break an undercarriage?
(1) Flare much too early, and stall in. Some professional knowledge added to a quick back of envelope sum tells me that to break a Cessna undercarriage you'd need a closure rate with the ground of at-least 10 ft/sec and probably nearer 14 ft/sec. That equates to a straight drop, with no lift acting at-all (which wouldn't be the case) .
(2) Land on a totally inappropriate surface, for example drift off the runway centreline and stick a mainwheel down a large rabbit hole. This does happen, but is not the undercarriage's fault.
A groundloop occurs when the pilot loses directional control of the aeroplane on the ground - this is almost impossible to achieve in a nosewheel aircraft and is largely a taildragger problem. When it does occur, a properly designed undercarriage should take it without any problems.
So, handle the aircraft as intended, and put it down on a runway surface each time, you can probably go your entire life without seeing an undercarriage failure.
G
Thread Starter
Joined: Feb 2005
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From: Vancouver
Hello,
Thanks for the reply. I noticed at normal glide to landing, the VSI reads almost 600ft/min. This is about 10ft/s with lift at the best range speed where you have the most L/D ratio.
I also noticed that if I flare too high, the sink rate after the stall is even sharper. So the straight drop should actually be more than 10ft/s. So if the main wheels do hit the ground if I did not add power, then it would be close to breaking the main wheel?
Thanks for the reply. I noticed at normal glide to landing, the VSI reads almost 600ft/min. This is about 10ft/s with lift at the best range speed where you have the most L/D ratio.
I also noticed that if I flare too high, the sink rate after the stall is even sharper. So the straight drop should actually be more than 10ft/s. So if the main wheels do hit the ground if I did not add power, then it would be close to breaking the main wheel?
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From: UK
That may to a large extent be perception, 600 fpm (10 ft/s) feels pretty benign at 1000ft and truly terrifying at 10 ft.
Yes, flaring at the right height is very important, but sit there and watch other student pilots flying circuits for an afternoon and you'll see a lot of pretty awful landings without anything breaking.
G
Yes, flaring at the right height is very important, but sit there and watch other student pilots flying circuits for an afternoon and you'll see a lot of pretty awful landings without anything breaking.
G
Joined: Mar 1999
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From: Vancouver, Canada
It would take some doing
I've been flight instructing on Cessnas for years in an area densely populated with Cessna-owning flight schools. I've seen a number of Cessnas with damaged nose gear (and accompanying firewall damage), but the worse injury I've ever seen to main gear is flat tires.
They can take a hell of a lot. When students flare too high, sometimes you just let them drop the airplane on, so the kick in the pants shows them they did something wrong and the instructor's lack of action shows them it's their own job to fly the plane. I will protect the nosewheel and kick the airplane straight so the gear doesn't have to take a side load, but otherwise the sprung steel does the job.
They can take a hell of a lot. When students flare too high, sometimes you just let them drop the airplane on, so the kick in the pants shows them they did something wrong and the instructor's lack of action shows them it's their own job to fly the plane. I will protect the nosewheel and kick the airplane straight so the gear doesn't have to take a side load, but otherwise the sprung steel does the job.
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From: "Home is were the answer machine is"
As an instructor I've been exposed to Cessna landings (well, arrivals really) that had ATC reach for the crash button. Often looks worse from the outside than from inside the A/C.
Joined: Mar 1999
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From: Vancouver, Canada
I just noticed that redblue and I are from the same city. Maybe he and I have "arrived" on runways together. If you're my student, redblue, you haven't even come close to breaking the mains.
Less thinking, more LOOKING at the shape of the runway exactly as your instructor flares, and copy that. In the flare, don't raise the nose any higher than needed to hold altitude. That way you won't start too high, and you won't balloon too high, so you needn't worry.
Less thinking, more LOOKING at the shape of the runway exactly as your instructor flares, and copy that. In the flare, don't raise the nose any higher than needed to hold altitude. That way you won't start too high, and you won't balloon too high, so you needn't worry.
Joined: Mar 2000
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From: Arizona USA
Older single engine Cessna aircraft have an issue with the spring steel landing gear legs used...not to mention the attach hardware used.
IF the improper type of paint stripper is used prior to a re-spray, it can cause 'hydrogen embrittlement' of the steel, thus affecting the strength thereof.
In addition, some of these gear legs need to be shot peened after maintenance, and if not done, can cause problems later on.
Reading the maintenance/overhaul manual usually answers these questions.
IF the improper type of paint stripper is used prior to a re-spray, it can cause 'hydrogen embrittlement' of the steel, thus affecting the strength thereof.
In addition, some of these gear legs need to be shot peened after maintenance, and if not done, can cause problems later on.
Reading the maintenance/overhaul manual usually answers these questions.
Joined: Sep 2001
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From: Toronto
As previously noted, the nose gear is stronger than the firewall.
I suspect the main gear is stronger than the fuselage, but have so far not gotten to that point.
Dropping it in from 3 feet is well tolerated by the airframe as I discovered when the optometrist added prisms to my prescription
I suspect the main gear is stronger than the fuselage, but have so far not gotten to that point.
Dropping it in from 3 feet is well tolerated by the airframe as I discovered when the optometrist added prisms to my prescription
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From: Somewhere between Cape Reinga and Invercargill
I did my first few hours to solo on a very tired Pa-38. This particular a/c had tread marks on the underside of the wing where it had landed so heavily that the tyres rubbed! I would love to claim responsibility for this 'arrival', but my finest moment was reshaping the tiedown on the tail when stalling it in from a few feet up and frantically trying to find more flare when there was none to be had!
Cheers
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From: Europe
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From: Oz
I know of case where a C206 had landed and shutdown. As the pilot stepped out onto the step the gear leg broke. Inspection revealed an existing crack at the fracture point. This was under the point where the step was bonded and had significant corrosion.
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From: las vegas
flight simulator landings are considered "crashed" if you hit the deck exceeding 300 ft/sec V/S .. so there must be a spec from someone - faa or one of the commercial airplane builders that says the design limits are as such .. those simulators are built to a rigorous spec ..
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From: UK
Given that the design limits are somewhere around 10-14 ft/s, 300 ft/s seems a little conservative on the part of the FS designers.
If it's 300 fpm, that would be a bit hard on the frame, but should be well within design limits for any aeroplane.
G
If it's 300 fpm, that would be a bit hard on the frame, but should be well within design limits for any aeroplane.
G
Joined: Apr 2005
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From: yyz
Ferried a 172 w/ the tube steel gear, that snapped the bolts holding the gear on. airbagged it up, put a spike in the hole did an expedient repair for the tailspar and flew it down to Mayo, Yukon. Young and Dumb!!!!
