737 going supersonic?
 

Guys,. .. .I read an article about a modified NASA 737-800, used for Shuttle approach work to Edwards. I the article it stated that the 738 was modified to get to 1.07 Mach or something like that. Is this possible or is this just journos getting their facts screwed up agin? I know the 777-200 was dive-tested to 0.96 Mach, but that's about it. Any info would be appreciated. Maybe a 737 driver could scare the hell out of their pax by trying it? <img border="0" title="" alt="[Wink]" src="wink.gif" />

Doubtful, but who knows for sure. The pylons and control surfaces would need major work. along with engine changes I would assume.. .. .I do know that they have converted DC-9s that can deploy the thrust reversers in flight and hang at a very steep angle of attack without meeting redline. It's getting them used to the steep angle of attack is what they are after not the speed. <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" />

Pilots training for a specific mission receive more intensive instruction in orbiter approach and landing in Shuttle Training Aircraft (STA), which are four Gulfstream II business jets modified to perform like the orbiter during landing. Because the Orbiter approaches landings at such a steep angle (17-20 degrees) and high speed (over 300 miles per hour), the STA approaches with its engines in reverse thrust and main landing gear down to increase drag and duplicate the unique glide characteristics of the orbiter. Assigned pilots receive about 100 hours of STA training prior to a flight, which is equivalent to 600 Shuttle approaches.. .. . <a href="http://www.wstf.nasa.gov/WSSH/Default.htm" target="_blank">Photo</a> . . <a href="http://quest.arc.nasa.gov/people/journals/aero/ringo/shuttle.html" target="_blank">NASA diagram & Trip Report</a>. .. .They also have a KC-135A, the "Vomit Comet", however, apart from some minor modifications to the hydraulic system to keep the pressure from dropping to zero during the periods of zero-G, the structure itself has not been strengthened, as the NASA missions are still within its normal certified operating envelope of +2.5/-1.0 Gs.. .. . <a href="http://www.avweb.com/articles/vcomet/" target="_blank">KC-135A</a>. . . . <small>[ 27 March 2002, 19:36: Message edited by: ORAC ]</small>

I'm not sure you would need to do a lot to go to Mach 1.07. When aircraft are being tested at 0.98 many parts of the airframe and the engine intake airflow are already supersonic. Obviously at 1.07 there is more stress on the airframe but I don't think there is a big jump at around Mach 1.

You might also want to read "<a href="http://www.avweb.com/articles/shuttle.html" target="_blank">The Day The Shuttle Landed Short</a>", an article over on Avweb about a failed shuttle simulator ride, which has a reasonable description of the energy management techniques the shuttle pilots use during approach.

It is thought that the 737-300 Silk Air Flight MI 185 probably reached close to, or at Mach One, in its fatal dive at high thrust - no speedbrakes and full nosedown stab trim.

</font><blockquote><font size="1" face="Verdana, Arial, Helvetica">quote:</font><hr /><font size="2" face="Verdana, Arial, Helvetica">. .When aircraft are being tested at 0.98 many parts of the airframe and the engine intake airflow are already supersonic.. .</font><hr /></blockquote><font size="2" face="Verdana, Arial, Helvetica">what part of the intake flow is supersonic? if anything a normal shock forms across the inlet face and pressure losses are incurred but flow will be subsonic thereafter(M~0.6 by design). the initial section of the inlet is a diffusing section designed to change the velocity into static pressure and reduce the speed of the air to M~0.4 which is usually what the first stage rotor can handle.. .. .if the flow was supersonic in the inlet, it would accelerate even more in the divergent section

Having never flown a heavy, i'm probably not best qualified to post on this subject, but one thing does strike me as odd.. .. .Wouldn't control surface problems prevent this from happening? if i remember correctly, don't you need an all flying elevator to overcome instability and loss of control at transsonic speeds? Don't 738 ( and most other heavies ) have standard elevators?. .. .Like i said, i'm not an authority, so please feel free to set me straight if i'm wrong. .. .WO

The 738 does have an all-flying tailplane if you count the way it trims the elevator. But some non-all flying tailplane aircraft, when properly designed, have no problems in the transonic\supersonic region. Anyone know anything about the stalling characteristics of the 738? Anyone tried to spin it?

I don't know about the 738 but back in 1991 my company had a 747 go supersonic after an autopilot induced upset. As I recall it went up mach 1.2 and only caused minor damage. Most of the damage was things like the fiberglass blowout panels on the top and bottom of the wing. The aircraft returned to service and flew several more years before being scrapped. Of course we nicknamed her "Christine". <img border="0" title="" alt="[Razz]" src="tongue.gif" />

Zoner:. .. .Ya forgot to mention the brown fog in the cockpit during and after the supersonic dive... <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" />

China airlines spun a 747SP, recovered and exceeded MACH 1 in the recovery, Aircraft landed sucessfully at San Francisco minus large significant bits of control surfaces and the airframe had to be retired.

not to mention most, if not all, big iron emply roll spoiler systems.. .. .nothing to ruin a day like aileron reversal!

Among other things the elevator system would have to be modified to overcome the mach tuck. Mach trim is done with the elevator alone and I'm not sure this would be able to overcome a true mach excursion.
(For the record 476EV had 1.084 mach on the FDR):)

Centaurus we did put the 737-300 sim through it once.

Started at FL370 at 48T GW with full throttle, giving us M.79 B.Pole. Initiated increasing spiral dive to the left with firewalled throttles and eventual full ND ( manual-range ) trim. This had us at M1.02 (fastest speed achieved in terms of Mach) passing FL240 at -92 deg pitch.

Man we went in like a bloodey bullet!