Re: Fastest airliner ?

From:         Brad Gillies <bradg@io.org>
Organization: Internex Online, Toronto, Ontario, Canada (416 363 3783)
Date:         08 Aug 95 01:45:11 
References:   1
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Here is the story of the fastest subsonic jetliner. I posted it here a
while back but here it is again.


               THE SUPERSONIC DIVE OF A DC-8
                  By William F. Smith, Jr.

  The article in the Fall 1990 American Aviation Historical Society Journal
by Dr.  Richard K. Smith in which he states the Pan Am Boeing 707 reached
.94 "a speed record that has not been exceeded successfully by another
subsonic airliner" is not so.

   On August 21, 1961, Douglas DC-8, N9604Z, was flown to a true mach of
1.012 at a pressure altitude of 41,088 feet. The speed was attained in a
dive in the Edwards Air Force Base area. The airplane was a DC-8-43 with
Rolls-Royce Conway Mark 512 engines modified to Mark 509 thrust rating.
The dive was initiated at a pressure altitudeof 50,029 feet (geometric
height of 52,090 feet). The purpose of this test was to achieve an altitude
of 50,000 feet and sonic speed. The airplane was a standard series 43
except for flight test instrumentation, a test airspeed boom on the right
wingtip. The wing had the four percent leading edge extension. At the
maximum altitude, the gross weight was 170,600 pounds (a w/s of 1,493,000).

  A pushover of 0.5g was held for approximately 15 seconds (22 degrees
pitch) and no airframe buffet was experienced during the acceleration to
mach 1.0. Takeoff thrust was used throughout the entire maneuver including
the pullout. The maximum true airspeed of 662.5 mph was attained at 39,614
feet pressure altitude. Prior to the dive, the stabilizer was trimmed such
that approximately a 50-pound push force was required to maintain the
stabilized dive. This was done to aid recovery because of the low elevator
effectiveness. The Askania Range at Edwards AFB was used to provide
geometric height.    The maximum observed mach on the production system
did not exceed .96 in the true mach 1.0 area.

  Recovery at 42,000 feet with full up-elevator gave no change in load
factor (also stabilizer trim would not function with this condition).
The pilot relaxed the elevator and changed the stabilizer trim from 0.5
degrees a.n.u. to 1.5 degrees a.n.u. This gave a 1.7 "G" and by 36,000
feet the airplane was recovered and decelerating below .95.

  This airplane became the property of Canadian Pacific where it operated
for many years. A plaque attesting to this accomplishment was displayed
on board the airplane.  Its whereabouts today is unknown as the airplane
was ferried to Miami where it resided for a time awaiting sale.

  The C.G. of 27 percent MAC provided an additional aid for recovery. An
F-100 photo chase plane and an F-104 pacer airplane accompanied the flight.

  A few interesting items during recovery. Buffet was experienced at 35,000
feet as the airplane was decelerating through .94 mach. During descent
through 42,000 feet at mach 1.0, rudder pedal buzz was noticed and
disappeared at 36,000 feet while decelerating. The rudder tab frequency
was 28 CPS, but the rudder surface was negligible. Aileron tab buzz of 36
CPS was also noted. The dive recovery was accomplished in about 5,000
feet.

  This flight was Bill Magruder's idea and he was the pilot. Bill also
planned a weight-lifting record but this was not done. I am always
surprised so few people were aware of this accomplishment. However, Douglas
did little to publicize the flight.  Our friend, Joe Tomich, was the flight
engineer.


Later...
Brad
AME(Canada), A&P(US)
Soon to be PP-ASEL