REFLECTOR: Falling objects through the prop

Sat Mar 12 00:51:51 CST 2005

Jim,
I don't have a parachute.  Since I agree with you that jumping from a
Velocity is not a high-probability operation, it's not worth buying a
parachute.  Therefore, I'll be flying the plane, too!
Keith

Jim Sower wrote:
"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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