Induced Pilot Error and Aviation Industry Ignorance

Date:         31 Jan 97 14:29:24 
From:         William Sherriff <>
Organization: AT&T WorldNet Services
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12018 Caminito Campana
San Diego, CA 92128
January 22, 1997

To:		Aviation Industry:

Subject:  	Induced Pilot Error and Aviation Industry Ignorance


Engineers failed to include a pitot heat system on the "Kiel" probe of
the X-31 aircraft that crashed after ice formed on the probe.  Evidently
they did not believe there was an icing problem in California?  There have
been at least three fatal accidents that I am aware of due to pitot-static
system icing or blocking.  The FAA has still not published a suggested
technique for control of the aircraft under these conditions.

The Boeing 737-200 series aircraft was designed with a short fuselage and
the resultant short longitudinal moment arm requires a large rudder for
control of the aircraft in an "engine out on takeoff" procedure.  Because
of the "uncommanded hard over rudder theory" as the cause of recent
accidents involving the Boeing 737, there are now directives to modify
and limit the allowable movement of the rudder.

This rudder modification directive indicates the possible requirement for
a change in the horizontal stabilizer design.  The amount of stabilizer
control is also affected by the short longitudinal moment arm and this
factor makes the Boeing 737-200 series aircraft more susceptible to the
"pitch-up" phenomenon!

A "pitch-up" is a natural reaction of a swept wing aircraft design to a
strong updraft.  The vertical component of the relative wind moves the
center of lift forward on the wing and raises the nose attitude.  This
happens on every landing when the aircraft enters ground effect and the
weight of the aircraft compresses the air creating a more vertical
component of the relative wind

The classic example of the weather induced "pitch-up: and the resultant
pilot induced upset accident is the Northwest Airlines Boeing 720B (8 feet
shorter than a Boeing 707, a significant factor) fatal accident near Miami,
Florida on February 12, 1963.  After two years of investigation the Civil
Aeronautics Board Report, (SA-372, File No. 1-0006 released on June 4,
1965) stated "The probable cause of this accident was the unfavorable
interaction of severe vertical air drafts and large longitudinal control
displacements resulting in a longitudinal 'upset' from which a successful
recovery was not made."

The Northwest Airlines crew had trimmed both the stabilizer and the
elevators full nose down accompanied by a strong forward control force on
the yoke upsetting the aircraft into a vertical dive.  This was an
experienced flight crew, the Captain had 17,000 hours and the Copilot had
11,000 hours flying time.  I would predict that any flight crew would have
reacted the same way under these conditions, having received the same
basic training in impending stall recoveries.

This report should be mandatory reading for pilots, especially those flying
swept-wing design aircraft.  The NTSB accident investigators and FAA
personnel were not aware of this report and the NTSB requested a copy from
me.  I told them it was available right there in Washington, DC.

The present prescribed approach and landing procedure require the pilot
to mechanically control a "rate of sink" with the resultant minimum
"control sense" feedback.  In this approach, because of the nose high
attitude required, the pilot does not have the landing area in sight in
the final stage of the approach!  In this approach procedure the inner
ear sensitivity to a steady state rate of sink is greatly reduced.  In an
article published in "Physics Today" Dr. A. J. Hudspeth, PhD, MD of the
Rockefeller Institute, states the following: "Constant velocity, e.g. a
constant rate of sink, has little ability to stimulate."

A Boeing Company study in the CAB report on the Northwest Airlines "upset"
accident near Miami, Florida on, April 12, 1963, states the following:
"The aircraft was recoverable from a 95-degree dive at 14,000 feet and
320 knots".

>From my experience in a vertical dive (free fall) in a Navy fighter type
aircraft I would challenge the Boeing Company to demonstrate the technique
for a successful recovery of a swept wing transport type aircraft from a
vertical dive.  The Northwest crew had 35 seconds to recover from 19,000
feet!  The aircraft came apart in the air!

In this same report the following statement appears, "Entry into an updraft
produces an initial aircraft response to 'weathercock' nosedown into the
relative wind.  However, it was pointed out that the ultimate effect of
the updraft is an altitude and noseup attitude increase."  In 36 years of
flying I have never experienced any aircraft design pitching down in an
updraft, initially or other wise.

The aircraft accident investigators of the NTSB rely heavily on the Flight
Data Recorder (FDR) readings to establish a "probable cause" for each
accident.  These readings however do not indicate the actual performance
of the aircraft.  They are the erroneous flight instrument indications
affected by the strong updraft that caused the attitude transition.  e.g.,
The reading in the Northwest Boeing 720B accident near Miami indicated a
9,000 feet per minute rate of climb!  In the COPA Airline Boeing 737
accident near Tucuti, Panama the FDR recorded instantaneous, radical,
attitude transitions that the Boeing Company stated were impossible for
the aircraft to perform!

In the Colorado Springs Boeing 737 accident, eye witnesses stated the nose
was rising just before the aircraft pitched over into a dive,, (ATC
controllers statement).  The investigators refused to recognize indications
on the FDR that the nose had risen because there was no increase in
aircraft load factor indicated on the FDR!  In a "pitch-up" there is little
or no increase in aircraft load factor, as I experienced in an
instantaneous "pitch-up" in a Boeing 707!

I am a retired Navy and Airline pilot with 20,000 plus hours of flying
time.  I believe I am the only pilot that has experienced this particular
combination of incidents.  A "pitch-up" in a Boeing 707 in visual flight
conditions, a true vertical dive (free fall) in a Navy fighter type
aircraft, and a crash of a Boeing 707 simulator in an unofficial "pitch-up"
exercise..  I have also used a "linear momentum" approach and landing
technique, resulting in dissipation of excess kinetic energy prior to an
imperceptible landing at less than the aircraft's actual weight.

Until the industry addresses the problems associated with the "rate of
sink" approach procedures, acknowledges the "pitch-up" phenomenon and
provides the required pilot training programs we will continue to
experience these accidents.  Until this required training is completed if
there is a finding of pilot error in these areas they must be referred to
as "induced pilot error".

William J. Sherriff
Captain (Retired)
American Airlines, Inc.