Supersonic 747
 

If you got a couple of brave chap(ette)s and strapped them into a 747, got it up nice & high and then stuck the nose far down with max thrust and hung on ..... would it -
- Go supersonic.
- Be controllable.
- Hang together.


From a discussion on another forum.

I'm no aviation expert, but I find the phrase 'Crash Horribly' comes to mind.

With a decent tailwind you'd get a supersonic groundspeed out of it. . . . does that count??! :E

i believe on the flight tests during dives well into the mach .9s were achieved. Also there was a major incident with a far east (china?) 747 yrs ago where they made a balls up of an engine flame out on the pacific.....between the farting around and doing nothing the aircraft ended up in a spiral dive and they reckon some of the control surfaces went supersonic.

Vne = 0.92 I believe.

Then you'd nose over into irrecoverable(?) Mach Tuck if its anything like the 737.

One DC-8-4X did reach Mach 1,012 already in 1960-s and recovered. A shallow dive as a part of deliberate flight testing.

They also had water ballast tanks AND pumps installed in the cabin to resist Mach tuck.

Can any subsonic plane recover from a Mach 1,000 dive without ballast pumps?

Which ones? Is 747 among them?

Well it's only another 30kts indicated from there to Mach One! :ok:

You first!

:ok:

Boeing tested the prototype up to M 0.991. I can't find anything that confirms for sure that the China Airlines SP went supersonic, in fact it seems more likely that it didn't.
The other thing that was talked about is that the engines would likely flameout.

To the best of my recall, the B747 is not fitted with a Mach Trimmer (cf the B707) therefore if the certifying authorities deemed it unnecessary then I presume that the handling at high mach nos` is benign. Remember also that demonstrated Vmd is quite a bit higher than Vne. Never was a problem demonstrating it in the sim on conversions however fidelity may be an issue here.

Link to video:
http://www.liveleak.com/view?i=e9f_1180909211

if its worth anything the GIV went supersonic in a dive during initial flight testing, or so i'm told

mmm.. if one was to attach some trent 900 engines instead of the Rolls 747 engines (provided they'd fit properly), add structural strength AND install some disposable, but strong rockets on the fuselage, could be a fun experiment!

(don't try this at home kids)

Why would any pilot want to take an aircraft beyond it's defined envelope?

During acceptence flights, I've taken the Classic to Vmo/Mmo, 392 KIAS/0.92 M. Between FL 26 and 29 in level flight advance to maximum rated thrust and accellerate. This usually produces something about 380KIAS. A slight push over will result in the 392/.92 rather quickly, with the over speed warning within 3 kts and .01 M. And thats what we want to see. Every once and a while you get a very slight burble or low rumbel as the air starts to go supersonic somewhere above the flightdeck.

Generally the intake airspeed of a jet engine does not like supersonic airflow. I would hate to see the dampage on the N1 rotors after any lengthy exposure to this rate of airflow and the boundary separation that would be occurring. As the airflow entered the N2 the engine would likely fail.

Want to go supersonic in a 747, go fly down wind in the jet stream, as previouly suggested.

You don't watch Top Gear then? :)

I have been supersonic a couple of times in a/c that had the airframe capability but not the thrust (no re-heat). I takes a lot of oomph to get throught the barrier. In both of the types the technique was to climb to fl450 then with full power roll inverted, pull the nose to 45 degrees down then roll right way up again. You were supersonic just long enough to say "wow hasn't it gone quiet and smooth" before pulling like hell to avoid making a bid hole and a nasty mess. G capability is much reduced when supersonic due reduced lift. Bearing this in mind I think the chances of getting a 747 supersonic and surviving it are pretty slim.

The Mythbusters will probably come up with the answer!!

Incidently if you ever achieve Mach tuck with the stick hard back and the pitch down continues, let it go under and roll out the other side - better than making a big hole in the ground.

C of P?
 

Not that I've ever flown the thing but?
Surely the thing would "take a dive" Cof P Where?( considering of course it had the thrust to push it through/displace the bow wave).
H/Snort

I don't believe anyone has suggested taking a 747 supersonic!

It's an interesting discussion though. I seem to recall it got a mention in the book, 'Handling The Big Jets'.

From what you posted Mustangsally, you're the only one here who has nudged the envelope! :)

Me too.

http://www.billzilla.org/highindicated.jpg

http://www.billzilla.org/reallyhighmach.jpg

The aeroplane handled just fine at those speeds.
The stabiliser trim should have more than enough authority to counter mach tuck - there's usually only about 4 units set in the cruise, with 9.0 available.