From: "Craig Wall" <email@example.com>
Subject: Accident at El Mirage
Date: 01 Oct 2000 20:28:14 GMT
Jeez- go away for a week and the idiots are at it again.
I know, to a reasonable *certainty*, what happened at El Mirage.
This posting will consist of three parts: 1) Proximate Cause; 2)
Underlying Cause; and 3) Why it will happen again.
1) Proximate Cause:
The pilot was performing a spin or pirouette-type maneuver with *power on*
at *near-zero airspeed*
This is an extremely dangerous maneuver for the following reason: a rapid
yaw with the disk tilted far back, if the pilot carries significant power
and simultaneously attempts to keep the nose up, amounts to a HUGE cyclic
input- far greater than can be otherwise accomplished with the controls
This will result in a VERY LARGE LOSS OF RRPM! Witnesses described a
"whooshing" sound. This occurs because the blades are being forced to fly at
very large angles of attack to try to re-orient the plane of rotation, as
commanded by the swing of the nose that is forcing the control head axis to
sweep out a cone.
This was NOT a PPO or an unprovoked blade failure! I have done similar
maneuvers and am only here to post this because I instinctively allowed the
stick forward. The light machines will yaw 180 degrees in under a half
second under these circumstances. Chuck Beaty tells me he did this once and
saw an instantaneous loss of 200 RRPM!!!!!
Holding the stick back is the wrong thing to do, and everything is MUCH
worse with more power, because the rotor is tilted so far aft in the first
place. This is NOT like the typical chandelle you see Kn Brock do at
airshows, where the disk is never asked to vary it's orientation suddenly-
this is like stirring the rotational axis through a cone in space. And
yes, we routinely swing the rotor axis sudden and far during steep tight
turns, but there we are applying a G-load that speeds the rotor up (or tries
to). In the "spin", it is all done at 1 G, so the sudden prying around of
the rotor control by the tail just practically STOPS the rotor!
The Underlying Cause:
Frankly, I lay this right at the feet of Bill Ortmeyer and the article he
posted a couple issues ago in Rotorcraft Magazine, where he described this
very maneuver! In that article he exhorted the reader to keep the stick
back so as to not let the nose drop!
It's a LETHAL and dimwitted article by someone who should not have a CFI
rating! I predicted at the time that this would result in deaths and it
took all of about 2 months. I voiced my concerns to Chuck Beaty at the time
and also to one of Ortmeyer's students, Steve Dix. I gave Steve very stern
warnings about how dangerous this maneuver is and how bad the advice was,
but to my horror and sorrow I let some other crap delay me in posting about
this on Norm's rotorcrat conference. I feel partly responsible for this
death, but be clear: this was insanity on the part of Rotorcraft Magazine
and Bill Ortmeyer for posting such an unexamined article. If it didn't
cause this death, it will cause others.
High mass machines may get away with this, because the yaw rates are less,
but an instructor should realize that a lighter machine can easily exceed
the allowable precession rates and cause a "precession stall", where the
rotor simply cannot keep up with what it's being asked to do and will simply
slow down and fold up. That is what happened here.
Why it will happen again:
This STUPID article is the result of a situation where instructors who
don't understand the principles of the machines they instruct in are
encouraged to become authority figures, because of the dimwitted belief that
a piece of paper makes an "expert".
Clearly Ortmeyer doesn't understand that, unlike a fixed wing airplane,
the rotorcraft does not have a fixed coupling geometry between the airframe
and the rotor- meaning the rotor can be doing one maneuver while the
airframe does something else. If he had, he'd have understood the reason
that there are times when you need to go into "stick-free" mode to prevent
yanking the rotor around beyond it's limits! That STUPID advice about
holding the stick back to prevent high airspeed on recovery is clearly
emotion bullshit: high dive-out speeds are hardly a concern when you are
starting at near-zero airspeed in the first place!!
Here's a BLUNT CHALLANGE!
Get me a KB-3. I will duplicate this accident at altitude and bail out
I have the expertise and the parachuting equipment to do this. I will do
it totally gratis, for either the PRA or the survivors of the man who died-
I don't care which, but someone has to put a stop to this insanity!
Naturally, it should be videotaped by a chase plane (I'd like to see Rusty
Nance and Bill Clem on that bird, but anyone else is free to volunteer), and
I will sign a complete liability waiver.
I'm calling you bastards out- this was an unnecessary death, and there
will be more if the PRA doesn't print an immediate retraction of that
article! You should at LEAST apologise to the survivors, and if you don't I
hope they sue the living shit out of you!
P.S.- I'm not looking for debate here- I *predicted* this, and the only
people I will respond to (in email) are my friends and anyone seriously
interested in performing the experiment with a sacrificial KB-3. I'm
finished with the asinine apologists for instructors who don't know *their*
ass from someone ELSE'S hole in the ground!!!