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 | | From: | Bertie the Bunyip | | Subject: | Re: Effect of spoilers on braking | | Date: | Thu, 25 Nov 2004 05:32:32 +0000 (UTC) |
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 | "tadchem"
sednews:dqGdnXyMKd0lKjzcRVn-2A@comcast.com:
>
> "AbsolutelyCertain" wrote in message
> news:cnr93g$1jr$0@pita.alt.net...
>
>
>
>> In other words, you made a guess. You don't know how many square
> (inches -
>> cm - feet - meters) of airplane are going to be sliding on the
>> ground.
> You
>> therefore don't know what the coefficient of friction is for that
>> combination of metal and pavement under the hypothetical conditions,
> because
>> you don't know the distribution of weight over the area without the
>> area. You don't know how the sliding and grinding action is going to
>> affect the area in contact with the ground, and thereby change the
>> coefficient of friction, and probably the contact area, as the event
>> proceeds. I think
> it
>> is also unlikely that the coefficient of friction is going to remain
>> constant as the airplane slows down. You don't have information
>> necessary
> to
>> calculate the stopping distance for this noisy experiment. You just
>> made
> a
>> guess. Nothing wrong with that, guessing is fun to do. But you
>> presented your guess as some sort of authoritative estimate and then
>> mocked people
> for
>> challenging your guess even though you had no way to back it up with
>> even the most rudimentary calculations.
>>
>> Did I miss anything?
>
> A few things...
>
> The rubber tire uses *static* friction as it *rolls* on the ground.
> The landing gear on large jets is designed to get the tires spinning
> *before* they touch ground so there is minimal torque on the wheel at
> the moment of touchdown. The weight applied to a pneumatic tire
> causes some deformation to the tire which is restored by the elastic
> properties of the pneumatic tire as it turns. This also heats up the
> tire. Other than a little bit of wear to the tread, no material is
> sacrificed.
>
> A landing skid uses *sliding* friction, an indeterminate amount of
> material is *always* lost. Germany actually tried this technique with
> a small aircraft during WWII, the Messerschmidt ME-163 "Komet", which
> had a 'deciduous' gear used for take-offs (it would fall away as soon
> as the plane was airborne). I understand the landings were as deadly
> to the pilots as fuel leaks (liquid hydrazine and 70% hydrogen
> peroxide). The problem was that the skid has no way to adapt to
> unevenness of the landing surface - even small pebbles could tear away
> large chunks of the skid, and buried stones (the Komet typically
> landed in open fields) could flip the plane.
>
> Look at the pictures...
> http://hans.liss.pp.se/ME163/
> http://hans.liss.pp.se/ME163/gallery/
> http://www.luftwaffepics.com/lme1632.htm
>
> Pictures showing a pilot beside the plane give a sense of the scale -
> these were really small planes!
>
>
The Germans also landed very large aircraft on skids.
the arado jet bomber, for instance,.
and then there was th eX-15..........
Bertie
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