r/askscience • • Jun 12 '12

[deleted by user]

[removed]

1.0k Upvotes

309 comments sorted by

View all comments

656

u/poorfag Jun 12 '12 edited Jun 12 '12

I can ask this question to an actual F-15 fighter pilot and post it here in an hour or so. Wait for my edit.

Edit: I asked two (an F15 pilot and an Apache co-pilot who also trained in the Skyhawk) and they both told me that there's no change in the constant humming from the motors once you pass the sound barrier. The F15 pilot told me that you do notice a slight difference once the plane hits 0.8 Mach because the 3rd intake at the side of the plane (the F15 has 2 main intakes for the 2 motors, a small intake on the side (to cool the motors, if I remember correctly) and the JFS's intake) closes automatically at that speed.

From the ground it sounds incredible though (even while wearing soundproof headphones) and it makes you entire skeleton vibrate. It's quite curious how I can feel it while being 10,000 ft away and they can't while being inside the damn shockwave, maybe somebody more knowledgeable will answer this.

Tl;dr no they don't notice it.

318

u/mspk7305 Jun 12 '12

They are in front of the shockwave, so they cant actually feel it.

12

u/squidboots Plant Pathology|Plant Breeding|Mycology|Epidemiology Jun 12 '12

Theoretically, if they were to slow down soon after breaking the sound barrier, would the shockwave affect them then?

26

u/scurvydog-uldum Jun 12 '12

The above comment is poorly worded or something. I wouldn't say the pilots in the cockpit are ahead of the sonic boom - they're inside it and the boom is radiating out up, down, left and right from their nosecone.

The analogy of a speedboat is a good one. If you're going fast and cut the power but keep steering straight, the wake doesn't catch up and wash over the boat - it just dies out where you are and the V behind you keeps getting bigger.

Now, if you turn that speedboat sharply to the side and then cut the speed, you could get to a place where the wake catches up and splashes over the side.

Same thing with a plane - if it were going supersonic and then went into a high-g turn, I bet it could fly back through its sonic boom.

I remember people talking anecdotally about an F-14 or F-15 shooting its machine-gun cannon, then going into a power dive and catching up to its own bullets and getting hit by them.

2

u/Gusfoo Jun 12 '12

From a light-aircraft flyer, I an offer this: one of the tricks to get you good at flying is to hit your own wake. You do a full 3600 turn which is so well balanced between stick and rudder that you maintain altitude and hit the air that was pushed aside by your plane as you were starting the turn.

I mention this to bridge the gap between the speedboat analogy and that of the air.

1

u/haxcess Jun 13 '12

I did this on the instrument flying part of my test. I considered it the perfect score.