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Are Airliners Capable Of Going Supersonic In Dive?  
User currently offlineHypersonic From United Kingdom, joined Oct 2005, 149 posts, RR: 0
Posted (5 years 10 months 6 days 6 hours ago) and read 9693 times:

Hi,
Considering that a lot of current airliners have cruise speeds between 80% - 85% of the speed of sound, & some of the larger ones & even the fastest biz jets can exceed 90% of the speed of sound in level flight..
Given that, if you were raking along.. then went full throttle, & put the aircraft into a steepish dive, would you most probably go supersonic & by how much?

I've read rumours that VC-10s' in RAF service, have been occasionally (accidentally on purpose  Wink ) pushed to just over mach 1 in level flight (or slight dive?) ?

Just curious
Hyper

49 replies: All unread, showing first 25:
 
User currently offlineOPNLguy From , joined Dec 1969, posts, RR:
Reply 1, posted (5 years 10 months 6 days 6 hours ago) and read 9697 times:

IIRC, Hoot Gibson's 727-100 sure did during it's dive some years ago...

User currently offlineA10WARTHOG From United States of America, joined Jul 2004, 325 posts, RR: 0
Reply 2, posted (5 years 10 months 6 days 5 hours ago) and read 9673 times:

Heard a rumor a Air China 747 did it.

User currently offlineEMBQA From United States of America, joined Oct 2003, 9364 posts, RR: 11
Reply 3, posted (5 years 10 months 6 days 5 hours ago) and read 9654 times:

A DC-8 did it too..... but keep in mind a commercial jet is not designed to fly supersonic and doing so is a very-very risky undertaking.


"It's not the size of the dog in the fight, but the size of the fight in the dog"
User currently offlineMalmi18 From Finland, joined Oct 2007, 13 posts, RR: 0
Reply 4, posted (5 years 10 months 6 days 5 hours ago) and read 9651 times:

Hi !

When I read this thread I remembered my young days and had to go and dig out a book from my youth (o those times!). "The Flier's Handbook" from 1978 says that "DC8-40 became the first airliner to exceed the speed of sound when, in 1961, it reached Mach 1.012 (667 mph) in a shallow dive". Sounds to me like it was intentional then.

And a bit of off-topic newsflash, the evening news said just now that the number of passengers on Finnair MD-11 increased by one in flight today, when a Swedish woman had a baby over Kazakstan. The plane was on the way from Bangkok to Helsinki. According to the news, the mother and the baby were ok so they continued all the way to Helsinki and didn't deviate to Moscow which was under consideration at some point.

Cheers and many more happy landings for both of them.

Malmi18


User currently offlineTyphaerion From United States of America, joined Jun 2005, 619 posts, RR: 4
Reply 5, posted (5 years 10 months 6 days 5 hours ago) and read 9647 times:
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The answer to your question is yes, it can happen, though the adverse affects that it can have on the aircraft structure and the engines need to be mentioned. When the flow goes to supersonic, it causes all sorts of pressure, temperature, and lift changes and all of these play havoc in a tight tolerace environment like the modern airliner.

Locally, with very little variance in the aircraft AOA or airspeed you can have areas that exceed Mach 1 dependant on the situation. Even within the engine, these local areas exceeding Mach 1 are possible, and sometimes are even designed to occur. Most of these are not good for the aircraft, but they do happen. For the entire aircraft to go supersonic, it would require even more deviation from the normal flight envelope, and the affects on the airframe would be worse.

But like everything else, it can happen, both by accident and on purpose. Though anyone who would put a 737 above Mach 1 on purpose has both reckless and stupid streaks in him as this is a very dangerous proposition. I have heard rumors from my former life, but none I will lead any credence too.



For some, the sky is the limit. For us, it is only the beginning... -- Jack Hunt
User currently offlineAjd1992 From , joined Dec 1969, posts, RR:
Reply 6, posted (5 years 10 months 6 days 5 hours ago) and read 9631 times:

Technically, if you fall from high enough, any aircraft can. Or, if you're high enough, the speed of sound becomes low enough it's easy enough to do, granted you have the power (which would be severely diminished at altitudes due to the thin atmosphere, I'm talking for a normal jet engine would run out of go at about FL550, even at the lightest of weights)

If, however, you are able to talk about it afterwards is a different matter  Wink


User currently offlineVikkyvik From United States of America, joined Jul 2003, 10035 posts, RR: 26
Reply 7, posted (5 years 10 months 6 days 3 hours ago) and read 9568 times:
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Quoting Ajd1992 (Reply 6):
Technically, if you fall from high enough, any aircraft can. Or, if you're high enough, the speed of sound becomes low enough it's easy enough to do, granted you have the power (which would be severely diminished at altitudes due to the thin atmosphere, I'm talking for a normal jet engine would run out of go at about FL550, even at the lightest of weights)

Well, once you hit the stratosphere, the speed of sound will start going up again, as the temp rises with increasing altitude in the stratosphere.

But airliners will only reach the lower reaches of the stratosphere now and then.



"Two and a Half Men" was filmed in front of a live ostrich.
User currently offlineKELPkid From United States of America, joined Nov 2005, 6388 posts, RR: 3
Reply 8, posted (5 years 10 months 6 days 2 hours ago) and read 9537 times:



Quoting OPNLguy (Reply 1):
IIRC, Hoot Gibson's 727-100 sure did during it's dive some years ago...

Hate to delve off topic here (and I've been trying to get an answer to this, but to no avail): This isn't the same Hoot Gibson that was a shuttle astronaut during the 1980's?

IIRC, the "Hoot" Gibson that OPNLguy is referencing was the one that is suspected of experimenting with in cruise slat deployment on a scheduled flight while the flight engineer was off in the can...the flight engineer fixed a few things (like pushed in circuit breakers which the captain and F/O had pulled) when he got back which sent the plane out of control...  Wow!



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineSEPilot From United States of America, joined Dec 2006, 6910 posts, RR: 46
Reply 9, posted (5 years 10 months 6 days 1 hour ago) and read 9528 times:



Quoting Vikkyvik (Reply 7):
Well, once you hit the stratosphere, the speed of sound will start going up again, as the temp rises with increasing altitude in the stratosphere.

But the increased temperature is more than counterbalanced by the decreased density. The speed of sound depends on both.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17041 posts, RR: 66
Reply 10, posted (5 years 10 months 6 days 1 hour ago) and read 9517 times:



Quoting A10WARTHOG (Reply 2):
Heard a rumor a Air China 747 did it.

IIRC this was the one with an engine that flamed out. During the subsequent dive it went supersonic. The pilots recovered the aircraft and landed it. It was missing quite a few parts. It was repaired and put back into service. I heard that it was never quite straight again.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineDeltaGuy From , joined Dec 1969, posts, RR:
Reply 11, posted (5 years 10 months 6 days ago) and read 9496 times:



Quoting Hypersonic (Thread starter):
& even the fastest biz jets can exceed 90% of the speed of sound in level flight

I know a few test pilots who have taken the G550 to about 1.02 or so. A plane with some huge engines and already high cruise speed can tend to do that.

DeltaGuy


User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 12, posted (5 years 10 months 5 days 23 hours ago) and read 9480 times:

Some misconceptions above.

The simple answer is yes, but the trick is recovering from supersonic flight and not damaging anything on your way through the number and back again.

For most types:

It would not take any dramatic nosedive to do it. In fact if you pitched down, say ten degrees or so from cruise you might well end up in Mach tuck and probably not recover.

It would not take any ungodly amount of power. Fact is we are throttled well back to keep it under .8 Mach, or so.

Troposphere/Stratosphere - probably not going to make much difference. The strat starts nominally at 36200' in standard atmosphere. Higher toward the equator, lower toward the poles etc. Below that, temperature (which determines the speed of sound) increases roughly 2°C per thousand feet of altittude loss. In the stratosphere up to any altitude the current crop of A or B airliners is likely to see, the temperature is isothermal. Eventually it may start rising again but that is all so theoretical in our discussion.

The way to go supersonic and recover is pretty much exactly the way the DC-8 did it in flight testing. A moderate push-over to unweight the wings and accelerate in a shallow dive, leaving you not too far below the horizon when you start to rein it all back in.

Here's that story:
http://www.dc-8jet.com/0-dc8-sst-flight.htm

My wife and I had dinner with Paul Patten one night and I did not know at the time that he was the man behind this. Too bad. I'd like to have talked about it. In fact I'd much rather talk about it than actually do it!



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineOPNLguy From , joined Dec 1969, posts, RR:
Reply 13, posted (5 years 10 months 5 days 23 hours ago) and read 9479 times:



Quoting KELPkid (Reply 8):
Hate to delve off topic here (and I've been trying to get an answer to this, but to no avail): This isn't the same Hoot Gibson that was a shuttle astronaut during the 1980's?

IIRC, the "Hoot" Gibson that OPNLguy is referencing was the one that is suspected of experimenting with in cruise slat deployment on a scheduled flight while the flight engineer was off in the can...the flight engineer fixed a few things (like pushed in circuit breakers which the captain and F/O had pulled) when he got back which sent the plane out of control... Wow!

Yes, that's something I should have clarified rather than assume folks knew that there were two different Hoots. The one on the 727-100 dive was a TWA guy. The NASA/Shuttle guy was a SWA guy.

Quoting Starlionblue (Reply 10):
IIRC this was the one with an engine that flamed out. During the subsequent dive it went supersonic. The pilots recovered the aircraft and landed it. It was missing quite a few parts. It was repaired and put back into service. I heard that it was never quite straight again.

I saw some photos of the 747 after they landed, and I recall that the main landing gear doors (upon departing the airframe during the dive) also took out the outboard 4-5 feet of each horizontal stabilizer...


User currently offlineViscount724 From Switzerland, joined Oct 2006, 25346 posts, RR: 22
Reply 14, posted (5 years 10 months 5 days 23 hours ago) and read 9454 times:

This is the Canadian Pacific DC-8-43 that went supersonic (Mach 1,012) in a dive from 52,000 ft. on a pre-delivery test flight in 1961. As a sidenote, in the 2nd photo it's carrying a spare R-R Conway in a 5th pod inboard of the #2 engine.


View Large View Medium
Click here for bigger photo!

Photo © Frank C. Duarte Jr.
View Large View Medium
Click here for bigger photo!

Photo © Gary Vincent



User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2556 posts, RR: 24
Reply 15, posted (5 years 10 months 5 days 21 hours ago) and read 9425 times:



Quoting Starlionblue (Reply 10):
IIRC this was the one with an engine that flamed out. During the subsequent dive it went supersonic. The pilots recovered the aircraft and landed it. It was missing quite a few parts. It was repaired and put back into service. I heard that it was never quite straight again.

It was rumoured to have gone supersonic, but according to the incident report it didn't even exceed MMO. The engine had a bleed valve fault causing asymmetry, but didn't flame out.

The TWA 727-100, though it was in a vertical dive, peaked at about 0.96 Mach according to the NTSB report.

http://www.airdisaster.com/reports/ntsb/AAR81-08.pdf



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineMax Q From United States of America, joined May 2001, 4524 posts, RR: 18
Reply 16, posted (5 years 10 months 5 days 19 hours ago) and read 9385 times:

Well, MMO on all the 727's I flew (In the less restrictive 'A' mode) was .92 Mach, so .96 is a fairly significant exceedance.

Having said that, the 727, like the 747 and other Boeing aircraft has superb high Mach characteristics and I think an excursion above Mach One would not cause an irrecoverable pitch down.

It is important to remember at these high Mach, albeit subsonic numbers there is already significant supersonic flow over considerable parts of the aircraft.



The best contribution to safety is a competent Pilot.
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 17, posted (5 years 10 months 5 days 19 hours ago) and read 9368 times:



Quoting Hypersonic (Thread starter):
Given that, if you were raking along.. then went full throttle, & put the aircraft into a steepish dive, would you most probably go supersonic & by how much?

Yep. But you won't get much over Mach 1 before something either fails or the drag gets so high that you stop accelerating.

Quoting SEPilot (Reply 9):
But the increased temperature is more than counterbalanced by the decreased density. The speed of sound depends on both.

No, it just depends on temperature. a = sqrt(gamma * R * T).

a = speed of sound
T = temperature (in K or F)
gamma = ratio of specific heats (1.4 for air at all but extreme temperatures)
R = gas constant

Tom.


User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 18, posted (5 years 10 months 5 days 9 hours ago) and read 9230 times:



Quoting Tdscanuck (Reply 17):
No, it just depends on temperature.

The simple version any pilot could use: The speed of sound is 39 times the square root of the air temperature in degrees Kelvin. No adujustment for "density" or "altitude" necessary.

Quoting Max Q (Reply 16):
.96 is a fairly significant exceedance

You sir are aptly yclept for this discussion.

M.96 is for sure something to approach with caution. Anything past MMO is test pilot-and-engineer country! For starters MachCRIT which is the point at which supersonic airflow will begin over some parts of the airplane is probably down around .74 or .75 so a 727 at .96 would be a crazy quilt of sub - and -super sonic air flow. You can have my share of it!



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2556 posts, RR: 24
Reply 19, posted (5 years 10 months 5 days 9 hours ago) and read 9226 times:



Quoting Max Q (Reply 16):
Well, MMO on all the 727's I flew (In the less restrictive 'A' mode) was .92 Mach, so .96 is a fairly significant exceedance.

Absolutely, but I felt it was important that urban myth was not posted as fact in Tech/Ops.



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2556 posts, RR: 24
Reply 20, posted (5 years 10 months 5 days 9 hours ago) and read 9219 times:

Of course, Concorde was capable of going supersonic in a climb.  up 


The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineTyphaerion From United States of America, joined Jun 2005, 619 posts, RR: 4
Reply 21, posted (5 years 10 months 5 days 9 hours ago) and read 9210 times:
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Quoting Jetlagged (Reply 20):
Of course, Concorde was capable of going supersonic in a climb.

Just not when painted any other color than white.  biggrin 

If and when they figure out how to play with the Mach wave better to decrease its destructive potential and noise, there will be supersonic airliners again. It isnt the technology to get the aircraft up to speed and keep it there that is the probelm, it is dealing with the affects of the compression wave that we cant handle.

Personally, I believe I will see supersonic jetliners in my lifetime.



For some, the sky is the limit. For us, it is only the beginning... -- Jack Hunt
User currently offlineSEPilot From United States of America, joined Dec 2006, 6910 posts, RR: 46
Reply 22, posted (5 years 10 months 5 days 7 hours ago) and read 9146 times:



Quoting SlamClick (Reply 12):
Here's that story:
http://www.dc-8jet.com/0-dc8-sst-fli...t.htm

There was distinctly some company propaganda in this article about the high speed characteristics of the DC-8. From what I have read the 707 flew faster and had better high speed handling; which is not surprising has Boeing had considerable jet experience with the B-47 and B-52 before the 707, and had their own high speed wind tunnel, while Douglas had to use the NACA tunnel. Besides, Boeing worked on the 367-80 for quite a while before Douglas committed to building the DC-8

Quoting Tdscanuck (Reply 17):
No, it just depends on temperature. a = sqrt(gamma * R * T).

I checked up on this and you are right. It turns out that density and pressure counteract each other, and so the only variable left is temperature.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 23, posted (5 years 10 months 4 days 6 hours ago) and read 8898 times:



Quoting SEPilot (Reply 22):
distinctly some company propaganda in this article

Well, it was written on Company time, on Company letterhead. I guess that should not surprise either of us.

Quoting SEPilot (Reply 22):
From what I have read the 707 flew faster

That is a statement that can have lots of meanings. I don't know much about either type but it certainly could be true for VMO and/or MMO and even higher cruise speeds in any corner of the charts, I don't know. I do know they occupied the same airspace system with a high degree of compatibility so I don't think the difference would have been too great. In absolute terms, however, the DC-8 did go faster. It was taken to a freestream mach number exceeding 1 and brought back, all intentionally and verified by an ubiased third party at Edwards AFB and the same is not true for the Boeing and that is that.

Quoting SEPilot (Reply 22):
had better high speed handling

Is that a quantifiable characteristic or someone's subjective observation?

Quoting SEPilot (Reply 22):
Boeing had considerable jet experience with the B-47 and B-52 before the 707, and had their own high speed wind tunnel, while Douglas had to use the NACA tunnel. Besides, Boeing worked on the 367-80 for quite a while before Douglas committed to building the DC-8

I wouldn't be too quick to dismiss Douglas' expertise in the area of high-speed flight:
World's fastest airplane for a time.


First airplane to exceed Mach 2 and thank you Scott Crossfield.


Okay, bad example. But if it had more powerful engines it might have set some records other than the highest liftoff speed (256 mph) and wickedest-looking design.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineOPNLguy From , joined Dec 1969, posts, RR:
Reply 24, posted (5 years 10 months 4 days 5 hours ago) and read 8868 times:



Quoting A10WARTHOG (Reply 2):
Heard a rumor a Air China 747 did it.



Quoting Starlionblue (Reply 10):
IIRC this was the one with an engine that flamed out. During the subsequent dive it went supersonic. The pilots recovered the aircraft and landed it. It was missing quite a few parts. It was repaired and put back into service. I heard that it was never quite straight again.



Quoting OPNLguy (Reply 13):
I saw some photos of the 747 after they landed, and I recall that the main landing gear doors (upon departing the airframe during the dive) also took out the outboard 4-5 feet of each horizontal stabilizer...

Yeek!

http://en.wikipedia.org/wiki/Image:D...ina_Airlines_Flight_006-N4522V.JPG


25 MarkC : One thing I do not understand. If a DC8 can do it, why would an F15C not go into a shallow dive at full non-afterburner power, go through the mach all
26 Jetlagged : Supercruise is about sustaining supersonic speed without afterburner, not passing Mach 1 without it. Concorde could supercruise across the Atlantic,
27 MarkC : I mean, I don't know, but you are saying that the F15C could not sustain supersonic speed after reaching it in a dive under non afterburning power? Or
28 Northwest727 : I think the 747-400 prototype may have broken the sound barrier, or at least approached it. I recall reading about how its wings were severely buffeti
29 DashTrash : I thought the X was the only thing that went that fast without an ejection seat. I'm crushed.
30 Tdscanuck : Fighters are, typically, aerodynamic messes. They're massively overpowered in order to have acceptable dogfight performance, so they can get away wit
31 Max Q : No, DashT, the 727 is a very fast aircraft, not a great climber but VMO was close to 400 knots and MMO .92 which I have done just for grins. Of course
32 DashTrash : The X is the same way. When it's light and cold, it climbs well. Heavy and warm, it's a pig until you find cooler air up high. It will haul once you
33 Jetlagged : The F-15 (C version or any other for that matter) could probably go supersonic in a dive without external stores, but it can't sustain it without aft
34 SEPilot : It did in that one flight; all that I have read (including the stats for both on the aircraft data section) say that the 707 was faster. It has more
35 A342 : While we're at it, what does the design dive speed of airliners say? It is higher than Mmo.
36 Tdscanuck : Why couldn't the DC-8 do it? It's a 1 g maneuver...with enough altitude it shouldn't have a problem. I took a look at the AFM for a 747...it doesn't
37 Post contains images SlamClick : You seem to be responding to something I never said or implied and using subjective hearsay in a technical discussion. I conceded that the 707 may ha
38 SEPilot : That is my point; of course it could. Just because nobody on record has does not mean that it can't. Just the same as the 707 going supersonic. Well,
39 SlamClick : I don't think that is what I said at all. Perhaps you would like to copy and paste a direct quote from one of my four posts, above to explain what yo
40 Post contains links A342 : Have a look at the A330 TCDS (page 12): http://rgl.faa.gov/Regulatory_and_Gu...c986257504005a9026/$FILE/A46NM.pdf "Maximum Operating Limit Speed/Mach
41 Tdscanuck : I think that's reversed. Vmo and Mmo meet at the transition altitude and, from there up, constant Mach number is decreasing absolute speed (since the
42 OldAeroGuy : Vd/Md are certified numbers. See FAR 25.335 for the relationship between Vmo/Mmo and Vd/Md. In the past, Vd/Md were demonstrated numbers. With today'
43 Viscount724 : I expect part of the reason for Pan Am ordering both the 707 and DC-8 initially was that both aircraft existed only on paper at the time (apart from
44 SEPilot : Quite true; however it does not change my opinion that the "supersonic excursion" was no less a stunt than the barrel roll. A whole company can colla
45 SXDFC : When I saw this topic, I could not help but think of UA 175, when it was on its collision course on 9-11, wasn't that plane passing the "red line" on
46 Tdscanuck : At those altitudes, you'd be speed limited, not Mach limited. You'd run out of speed before you went supersonic. Tom.
47 Starlionblue : Indeedy. IIRC they were flying fast enough to potentially damage the aircraft, but nowhere near the speed of sound.
48 Viscount724 : Of the 25 DC-8s ordered by Pan Am I believe 4 were assigned to Panagra and 2 to Panair do Brasil, then both partly-owned by Pan Am (50% in the case o
49 SEPilot : That makes sense; and the one I referred to earlier that left the fleet in 1962 went to one of those (I forgot which.) But the bottom line of it was
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