Comments on: Is it possible for a Commercial airline to break the sound barrier?

By: grumpy geezer

grumpy geezer — Mon, 16 Nov 2009 09:38:59 +0000

Gergely and Kevin are correct. The date of the DC-8 going supersonic was August 21, 1961. It happend on a test flight. It was done intentionally.

Wind wouldn’t affect the outcome.
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By: Kevin Z

Kevin Z — Mon, 16 Nov 2009 09:00:59 +0000

Yes it would. I Douglas DC-8 has done it in a vertical Dive
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By: Cap'n M

Cap'n M — Mon, 16 Nov 2009 08:13:59 +0000

The answer is yes, the Concorde used to go supersonic - only over oceans (due to the ‘Sonic Boom’.)

However, nowadays, there are no commercial aircraft (there are military aircraft) that are commissioned to go supersonic, however as mentioned above, with a tailwind, max thrust and probably rapid decent, the aircraft could go supersonic - whether the aircraft sustains the forces involved is another matter.
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Sonic Boom: http://en.wikipedia.org/wiki/Sonic_boom.

By: Techwing

Techwing — Mon, 16 Nov 2009 07:46:59 +0000

A tail wind does not increase the airspeed of the aircraft, so it would not push an aircraft beyond the sound barrier.

Commercial airliners will not necessarily break up at the speed of sound, but they may suffer structural damage. They have broken that barrier accidentally on some occasions, in dives during emergencies, and in tests. The aircraft are not designed to fly smoothly and efficiently at speeds at or above the speed of sound, but they can probably survive a brief excursion to supersonic speed. Of course the aircraft would have to be thoroughly inspected and possibly repaired (or even scrapped) after such an event, just to be on the safe side, even if it didn’t break up.

Commercial airliners often have a smooth but very blunt nose. It turns out that this type of nose is more efficient at speeds below the speed of sound, but it’s much less efficient at supersonic speeds. Conversely, an aerodynamic shape that is efficient at supersonic speed may simply produce too much unnecessary drag at subsonic speeds.
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By: Flight Instructor

Flight Instructor — Mon, 16 Nov 2009 07:31:59 +0000

At speeds greater than this, drag increases rapidly. So this tends to be a practical limit. On the other hand, with a swept wing it is possible to get small areas on the wing where air flow is trans-sonic (a very dangerous condition). As a previous writer stated, having a tail wind (or a head wind) would have no affect on airspeed.
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By: Davsters

Davsters — Mon, 16 Nov 2009 07:23:59 +0000

I believe only Concorde has done that. None of the Commercial airliners currently in operation do that I don’t think.
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By: Gergely

Gergely — Mon, 16 Nov 2009 06:57:59 +0000

First, a tailwind (or any wind) does not influence the Mach number, as the Mach number depends on the plane’s speed in relation to the air, and not in relation to the ground.

Second, yes, it could go past the sound barrier (e.g. during a steep descent), but if it is not specifically designed for supersonic operation (like the Concorde), the wings and engines would stall. It wouldn’t break up, but it might suffer some structural damage. Once a DC-8 reached Mach 1.012 during a controlled dive, but in the end they landed it safely.
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By: They call me ... Trixie.

They call me ... Trixie. — Mon, 16 Nov 2009 06:21:59 +0000

The Concord used to do it all the time, but they weren’t allowed to do it over land: they had to be over the ocean. Air France and British Air both flew planes at supersonic speeds.
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By: Petero

Petero — Mon, 16 Nov 2009 05:40:59 +0000

In an uncontrolled dive, it would be, but I believe the aircraft would probably start to break up!
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