REFLECTOR: Falling objects through the prop
Jim Sower
canarder at frontiernet.net
Fri Mar 11 13:55:56 CST 2005
<... since opening the door will likely start a roll ...>
Opening the door actually causes the door to instantly depart the
airplane. The open hatch also causes MAJOR drag (when I lost my pax side
door on TO, I barely had power enough to make it downwind to a 500'
abeam position). I think that absent power (why else would anyone want
to bail out) you'll be looking at a serious sink rate.
All things considered, I think I'll opt to fly the airplane ... Jim S.
KeithHallsten wrote:
> Al,
> When it comes to parachuting out of an elite-door Velocity, I would
> want to make sure I got a good push off of the door sill on the way
> out! Also, since opening the door will likely start a roll, you
> wouldn't want to waste any time in making your departure.
> 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 9:02 PM
> *Subject:* RE: REFLECTOR: Re: Falling objects through the prop
> (Was NOSE WHEELGOTSIDEWAYS)
>
> 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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