Engine noise forward of engines at mach 1+?

Matt13C

Matt13C

Well-Known Member
When sitting in a traditional commercial aircraft, you can hear the engine noise while in cruise flight. If they brought back the Concord or another mach 1+ capable commercial aircraft, once the jet passed through mach 1, would everyone forward of the engines not hear them any longer? I imagine that the air against the hull at those speeds would create a good deal of noise also.

What is the experience in a fighter at mach 1+?
 
Sound would be transmitted from the engines, through the airframe, and into the air in the cabin, all of which are moving at Mach 1+. So yes inside the cabin you would still have engine noise.
 
Roger Roger said:
Sound would be transmitted from the engines, through the airframe, and into the air in the cabin, all of which are moving at Mach 1+. So yes inside the cabin you would still have engine noise.
Click to expand...

But that's all you would hear. The noise through the airframe. Anything not transmitted through the airframe would now be behind you.
 
Autothrust Blue said:
No firsthand experience, but I'd believe "YEEHAW" is the experience.
Click to expand...

Unfortunately, there is no sensation of speed up at altitude, which is where the majority of super flight takes place. I have only been supersonic down close to the ground a handful of times, and it can be pretty spectacular.

A supersonic fighter generally handles like a speedboat that is up on plane -- it has very sluggish maneuverability and also feels pretty mushy in the controls. All in all, distinctly non-exciting in that aspect.

There is no difference in sound inside the cockpit when traveling supersonic. Some aircraft have differences in wind rush noise over the canopy at varying speeds, but those sounds change with indicated airspeed and not Mach number. In the Strike Eagle, up close to 500 knots indicated is usually when we would start hearing significant wind rush over the canopy. Most of the time supersonic up at altitude, the indicated airspeed was less than 350 knots.
 
To pile on Hacker's comment about the Dark Gray Warhorse... You wouldn't know you were supersonic if you weren't staring at the Mach No and G-Available (which changes into what's called the "thumbprint" in the transonic region).

Also, in the Strike Eagle, you may get some aileron flutter prior to passing the number... a very small amount is normal, but obviously not prolonged or excessive deflection.

One thing that is noticeable.... very much so... is the deceleration when you pull the power out of max AB to idle above the mach. It's like smoothly slamming on your brakes at 100mph in your car.
 
mshunter said:
But that's all you would hear. The noise through the airframe. Anything not transmitted through the airframe would now be behind you.
Click to expand...
I don't think that is correct... noise coming from the compressor and engine would still travel forward at its normal speed relative to the speed of the aircarft.

There was a made for TV movie about the Avro Arrow starring Dan Akroid and they had a scene in the cockpit where the test pilot took a female engineer up... when they passed thru mach 1 everyting went silent, and his exlanation was that they were outrunning the sound. Totally BS.

Its just like throwing a baseball forward from a truck that is doing mach 1... the ball will be travelling at whatever speed you imparted on it + Mach 1.
 
Hacker15e said:
Unfortunately, there is no sensation of speed up at altitude, which is where the majority of super flight takes place. I have only been supersonic down close to the ground a handful of times, and it can be pretty spectacular.

A supersonic fighter generally handles like a speedboat that is up on plane -- it has very sluggish maneuverability and also feels pretty mushy in the controls. All in all, distinctly non-exciting in that aspect.

There is no difference in sound inside the cockpit when traveling supersonic. Some aircraft have differences in wind rush noise over the canopy at varying speeds, but those sounds change with indicated airspeed and not Mach number. In the Strike Eagle, up close to 500 knots indicated is usually when we would start hearing significant wind rush over the canopy. Most of the time supersonic up at altitude, the indicated airspeed was less than 350 knots.
Click to expand...
ad0oeq.jpg
 
What if you were cruising at say, .80 Mach up at altitude and you had a 150+ kt. tailwind which put your groundspeed supersonic. Would the people on the ground hear a sonic boom?
 
Proud Pilot said:
Learn something new everyday. My professor told me it would.
Click to expand...
The question makes my head hurt like airplane on a treadmill... When I really think about it.

My understanding is primitive, but i thought

Mach is your airspeed divided by the relative speed of sound where you are in any fluid.

Or the speed of an object moving through a fluid. Since tailwind or headwind do not affect your airspeed they do not affect your speed through that fluid since it's all relative, only your speed over ground which is irrelevant.

So theoretically you could break the speed of sound with 0 knots of ground speed?

I'm not smart enough for this stuff
 
jwp_145 said:
I don't think that is correct... noise coming from the compressor and engine would still travel forward at its normal speed relative to the speed of the aircarft.
Click to expand...

No, it will not. That's not how it works. Sound is propagated through the air. If you're ahead of the sound source and going faster than sound waves can propagate then the sound will never reach you.

jwp_145 said:
There was a made for TV movie about the Avro Arrow starring Dan Akroid and they had a scene in the cockpit where the test pilot took a female engineer up... when they passed thru mach 1 everyting went silent, and his exlanation was that they were outrunning the sound. Totally BS.
Click to expand...

It is total B.S., but not for the reason you cited. As previously noted, sound (in the form of vibration) is still propagated through the airframe and then transferred to the air in the cockpit. Sound travels through solids at much faster speeds than through gases or liquids, so Mach 1 becomes irrelevant in this case.

jwp_145 said:
Its just like throwing a baseball forward from a truck that is doing mach 1... the ball will be travelling at whatever speed you imparted on it + Mach 1.
Click to expand...

Nope. Instead of making the baseball analogy, use another wave propagation comparison — light. Even if you're traveling at .99% of the speed of light and then turn on a flashlight in the direction of travel, light still travels at the universal constant. It does not leave the flashlight at C+.99C.
 
Last edited:
Vector4Food said:
So theoretically you could break the speed of sound with 0 knots of ground speed?

I'm not smart enough for this stuff
Click to expand...
You'd still have to update your TAS with ATC!

That rule seems antiquated now with fancy algorithms that spit out flow control to ARTCC facilities, at least down here. Not sure if NavCanada uses a similar system.
 
You must log in or register to reply here.
Back
Top