53

Is it possible for the pilot to feel passing through the sound barrier in an F-16?

What about other modern aircraft, will you feel anything? Do you need to go back to really dated designs before you can notice this, is it a problem of the past, or did the documentaries I watched which discussed this problem grossly exaggerate it?

AlphaCentauri
  • 3,987
  • 4
  • 23
  • 42
  • 2
    FWIW, the sound "barrier" is not so much a thing that an aircraft encounters in flight as it was an obstacle that aircraft designers faced before they fully understood the nature of supersonic flows, and learned how to build aircraft that were capable of controlled, supersonic flight. – Solomon Slow Aug 23 '19 at 14:08

3 Answers3

59

In an aircraft designed to go supersonic, it's an absolute non-event, and one is only aware of it by observing the instruments, and noting diminished control authority-- slower roll rate, etc. At least, that was my experience in the T-38, and according to every account I've read.

If the aircraft is NOT designed to go supersonic, then the experience can be quite different, although that mostly comes from loss of control at high Mach numbers (starting in the 0.9X range, as best I recall), rather than anything that occurs right at Mach 1.00.

Ralph J
  • 51,356
  • 17
  • 157
  • 249
  • 2
    I've heard of the P-38s going transonic in dives and not being able to recover until they can get into denser air. – BillDOe Aug 20 '19 at 18:38
  • Thank you for your answer. Are you saying that there is a sudden jump (or rather, a fall) in control authority once passing mach 1? So in the T-38, going from mach 0.9 to mach 1.1 results in a much greater loss of control authority than going from mach 0.7 to mach 0.9, in the same aircraft? – AlphaCentauri Aug 21 '19 at 00:42
  • 3
    Generally, the T-38 had an amazing roll rate, like over 360 degrees per second. Supersonic, though, it was way less, maybe a quarter or an eighth of that. Don't remember exactly when it dropped off; it was NOT a noticeable thing at Mach 1; you noticed a twitch in the airspeed & altitude indications, but only that. Then you try the aileron roll, and it seems to take forever. We didn't demo that at .90, .95, etc for comparison, unfortunately. – Ralph J Aug 21 '19 at 02:06
  • 2
    @BillDOe: There is no recorded case of the P-38 going faster than sound. There were problems in high speed dives that cause loss of control, but they were not caused by the P-38 breaking the sound barrier. There were P-38s that broke up in dives. The "bang" from the breakup was (falsely) interpreted as a sonic boom. – JRE Aug 21 '19 at 11:40
  • I wonder what it would feel like in an A320... – Cloud Aug 21 '19 at 12:23
  • @Cloud I think that the answer explains that – Federico Aug 21 '19 at 12:37
  • 14
    @JRE He said transonic, not supersonic. The loss of control authority on P-38s in high speed dives was related to parts of the airflow around it becoming supersonic (but I agree definitely not the plane as a whole), see https://en.wikipedia.org/wiki/Mach_tuck – llama Aug 21 '19 at 16:29
  • 2
    Doesn't it get a little quieter in the cockpit at supersonic speeds? – Mike Waters Aug 22 '19 at 16:12
  • Yeah, that's what I was going to say. Would the wind noise decrease? Or is there just no audible wind noise in the first place? – user45266 Aug 22 '19 at 17:29
  • @JRE, the term I used was transonic, not supersonic. I've always understood the former to mean that some parts of the airflow are forced to move at supersonic velocities, while the plane itself is still subsonic. This then causes compressibility issues that deflect normal airflow away from the plane's control surfaces. – BillDOe Aug 23 '19 at 00:11
  • 1
    Does anyone have good detailed data recordings from a modern jet transitioning into supersonic speeds to add to the answer? Scientific measurement kind of data I mean. [I spent some time in the back of an F-18 on research flights, and could hear/feel subtle differences based on speed, but given that I can hear far lower than average frequencies I'm probably a terrible data point...] – TheLuckless Aug 23 '19 at 16:38
24

You can watch for yourself 4 minutes in on this video. Can't tell at all, so much so that they have to let people know with a big sign. Once the issues of buffeting during the transition were fixed in the design of supersonic aircraft, pretty anticlimactic.

user
  • 6,984
  • 2
  • 29
  • 66
John K
  • 130,987
  • 11
  • 286
  • 467
6

In the F-18, you experienced a very slight "tuck", which was basically the nose of the aircraft pitching around the horizontal axis very slightly. But, it was extremely minor, and in order to notice it you needed to be in smooth air, and paying close attention.

In 99% of transitions through "the number", you were so focused on other stuff you noticed nothing.

Rodrigo de Azevedo
  • 1
  • 1
  • 9
  • 28
RoryH
  • 411
  • 3
  • 3
  • 1
    Very interesting answer. Perhaps you could add the source for this? It seems implied that you either are or were an F/A-18 pilot, is this true? Or it this second hand information from someone else? – AlphaCentauri Aug 25 '19 at 14:32
  • 2
    I am the source, so indeed it is hard. I flew F-18's for the Australian Air Force in a past life. – RoryH Aug 27 '19 at 10:50
  • 1
    Thank you for your comment, and answer. – AlphaCentauri Aug 27 '19 at 19:31