B737 RUDDER FAILURES |
John King wrote: Subject: Re: USAIR Flight 427 B737's Rudder - Hardovers
and HardtoSwallows |
Subject: FAA's McSweeny statements contradict FAA
own Team Findings
Date: Sat, 13 Mar 1999 07:53:41 -0500
From: John King <jking1@mediaone.net>
To: IASA Safety <safety@iasa.com.au>, David Evans <devans@phillips.com>,
Edward Block <EdwBlock@aol.com>, lyn romano <rosebush2@hotmail.com>,
Patrick Price <PAPCECST@aol.com>, Timothy Clark <timothyclark@compuserve.com>,
max lenz <hau-if@datacomm.ch>, res gehriger <res.gehriger@sfdrs.srg-ssr.ch>,
Tim van Beveren <tvb1@prodigy.net>, Ader
<ader@compuserve.com>,
Bob Rowland <rwroland@aol.com>, "BabsF342@aol.com"
<BabsF342@aol.com>,
Kay Pennington <KPennington@prodigy.net>
To All:
FAA's Tom McSweeny has omitted in a public statement the FAA's own
team findings that electrical malfunctions may have caused these
unexplained 737 rudder hardovers. (This is not the first time Mr.
McSweeny's statements have contradicted FAA or industry data.)
This present contradiction can be seen by reading a reference to that
FAA team finding within a document by the Airline Pilots Association
(ALPA) and by reading a McSweeney's most recent FAA statement by
McSweeny on March 11.
Two articles are linked here regarding this ongoing 737 rudder
controversey. The first article is ALPA's submission to the NTSB
regarding U.S. Air flight 427.
View this at http://airlinesafety.com/articles/ALPA2.HTM
Scroll to - section d; "FAA Critical Design Review Team" (CDR)
Scroll to - "A visit to Honeywell/Sperry by a CDR team representative
resulted in two observations:"
Scroll to - " 2. There are a number of failure modes that could cause
the Yaw Damper to command a rudder deflection to the Yaw Damper
authority:
Note the team findings of;
"a. Electrical shorts of grounds,"
"b. Open feedback circuit, and ..........."
The second article, By Tim Dobbyn (Reuters) was posted in Washington,
March 11 at 11:28 PM ET. This article title was; "FAA
says Boeing 737 rudder redesign unwise".
Statements, by McSweeny, omit these FAA team findings of any electrical factors that
could explain these hardovers.
See this article at
http://www.infobeat.com/stories/cgi/story.cgi?id=2558773429-160
The text of this article and McSweeny's statements also follow.
"The Federal Aviation Administration said on Thursday that a major redesign of the
Boeing 737 rudder was unnecessary and could pose risks of its own. The National
Transportation Safety Board (NTSB) is considering recommending design changes at a meeting
scheduled for later this month on the probable cause of a 1994 USAirways crash near
Pittsburgh.
FAA Associate Administrator Tom McSweeny said his agency had already addressed the three
most likely scenarios for that crash with modifications to the 737 rudder and pilot
training.
"We've looked at the data. We think there are three scenarios that could have caused
this accident and we've dealt
with all three of them," McSweeny said. Major rudder changes would force a whole new
system into an existing airframe at repair stations around the world.
"I think the risk of unintended consequences is real," McSweeny told reporters.
There are more than 3,000 Boeing Co. 737s in service around the world and about 1,300 of
them are registered in the United States. The NTSB can only make recommendations to the
FAA, whose rules are usually adopted by other aviation regulators around the world.
USAir Flight 427 was about to land at Pittsburgh International Airport on Sept. 8, 1994,
when it rolled sharply and dived into the ground, killing all 132 people on board.
Computer simulations of the accident show the plane's rudder, the hinged rear portion of
the vertical tail fin, went hard to the left just prior to the crash.
What caused that rudder movement is still the subject of debate. The 737 rudder is also
suspected in a 1991 crash of United Airlines Flight 585 near Colorado Springs, Colorado,
that killed all 25 people on board.
An Eastwind Airlines 737 in 1996 experienced an in-flight upset but recovered safely. On
Feb. 23, a USAir Metrojet experienced an unintended rudder movement while at cruising
altitude. The flight diverted safely to Baltimore-Washington International Airport.
McSweeny is not convinced the two accidents and two incidents have a common cause, but he
believes the FAA's initiatives since the Pittsburgh crash have sharply reduced the
likelihood of two types of unintended rudder movement or pilot error.
A new design of hydraulic power control unit, which all U.S. operators are required to fit
by Aug. 4 this year, eliminated the possibility of a mechanical reversal of the rudder
controls found in post-accident research, McSweeny said.
A new digital yaw damper system and hydraulic pressure reducer, to be retrofitted to all
older 737s by July 2000, will further limit the potential for a major in-flight upset. Yaw
is a side-to-side wiggle along the length of the plane and is
suppressed with small rudder inputs, mainly for passenger comfort.
The FAA has encouraged programs to train flight crews how to recover from unusual flight
attitudes, but it has not yet made the sessions mandatory.
The NTSB is due to meet on March 23 in Springfield, Virginia, to discuss the USAir Flight
427 crash."
END TEXT-----------
Please circulate to any other interested paties not listed here.
Thanks,
John D. King