REFLECTOR: Re: Falling objects through the prop (Was NOSE WHEEL GOTSIDEWAYS)

[Jim Sower]

<... person could safely parachute out of an elite door Velocity ...>
I think the gear had best be retracted ... Jim S.

Al Gietzen wrote:

> Keith;
>
> Yes, I realized as I went back out to the shop that my 
> “thinking-out-loud” analysis was all wrong; so I’m glad you followed 
> up. At first your 1.4 inches seemed too small, but the math is 
> correct. I think the fact that the object is initially at the speed of 
> the plane makes a huge difference, and makes it likely a small metal 
> object (small and dense) would clear the prop, probably by some 
> margin. It only needs a ¼ of a second to make it.
>
> Some time ago I remember doing some back-of-the-napkin analysis with a 
> couple of Long EZ drivers which concluded that a person could safely 
> parachute out of an elite door Velocity, but it may have been a 
> somewhat used cocktail napkin.
>
> Al
>
> *Subject:* REFLECTOR: Re: Falling objects through the prop (Was NOSE 
> WHEEL GOTSIDEWAYS)
>
> Al,
>
> I follow you up through the point where you say the object will only 
> fall 85 msec before the prop comes by. However, as I recall the 
> position formula is:
>
> X = X(init) + V(init)*T + 1/2 A*T*T. If we use the initial elevation 
> of the object as our datum, X(init) = 0, and if the initial downward 
> velocity, V(init), is also zero. If we further assume that the only 
> acceleration acting on the object is gravity (32.2 ft/sec^2), then
>
> Distance Fallen = 1/2 * (32.2 ft/sec^2) * (0.085 sec) * (0.085 sec) = 
> 0.117 ft = 1.40 inch.
>
> So does your prop arc extend lower than 1.4 inches below the level of 
> your nose gear door? Sure!
>
> However, we have neglected the fact that any object that falls off the 
> plane is initially at the speed of the plane, not at rest, and it is 
> slowed by air friction, so it is decelerating horizontally while is is 
> accelerating vertically downward. If we know the drag coefficient of 
> the object that's falling, we could calculate that deceleration due to 
> the relative wind, but that will be left as an exercise for the 
> reader! Suffice it to say that the object will actually fall 
> significantly longer that 85 msec, and will therefore fall farther. If 
> the prop arc extends, say, 16 inches below the belly of the plane, we 
> would need to have approximately 1.0 second of fall to clear the prop 
> arc. Is this likely? Probably not.
>
> I think the conclusion is that anything that falls off the fuselage, 
> even from the nose, is pretty likely to pass through the prop arc.
>
> Keith
>
>     ----- Original Message -----
>
>     *From:* Al Gietzen <mailto:ALVentures at cox.net>
>
>     *To:* 'Velocity Aircraft Owners and Builders list'
>     <mailto:reflector at tvbf.org>
>
>     *Sent:* Thursday, March 10, 2005 8:08 AM
>
>     *Subject:* RE: REFLECTOR: RE: NOSE WHEEL GOT SIDEWAYS
>
>     *Subject:* REFLECTOR: RE: NOSE WHEEL GOT SIDEWAYS
>
>     Tom
>
>     You say believed you lost the "T" fitting in flight. Did you check
>     the Velocity high speed rotating strainer that's attached to the
>     engine to see if it was detected, evidenced by leaving 'memory
>     marks'? Idle curiousity: Can anything fall off the plane's
>     fuselage without going through the prop at rotation speeds or above?
>
>     Chuck
>
>     Well, let’s see; at 120 mph that’s 176 ft/sec – so it takes about
>     85 msec to travel 15 ft. If you drop something from the nose gear
>     well, it will travel downward a max of about 30 – 35 in. before
>     the prop goes by. It might clear the prop.
>
>     Just thinking out loud, check my math.
>
>     Al
>
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