12

enter image description here
(YouTube)

In the frame above the pilot is pulling back, as evident by the stabilator's position, and this technique is usually cited as a means of slowing down.

But wouldn't the brakes have better effect if the struts are fully compressed as with jet-liners? What makes aerodynamic braking effective for jet-fighters then?

Clarification:

Presumably that fighter pilot is applying some brakes at least (otherwise they wouldn't have added a drogue chute).

My thinking is, if the nose gear was planted, the same braking force will have a better effect (reduced lift), even without spoilers present since the jet engines won't be contributing to the struts decompression. Also the nose tire will add to the rolling friction.

  • 1
    Using wheel brakes while aero-braking would slam the nose gear to the runway - that’s bad! Aero-braking is all about drag, not wheel brakes. Works well on some aircraft, not well at all on others. – Ralph J May 23 '18 at 23:02
  • I wonder if this nose up landing attitude would be practiced even if aero braking weren't needed, to keep the intakes out of the dirt. This aircraft was intended for rough airstrips. – Pilothead May 24 '18 at 00:26
  • You are probably right, which is why in your linked wiki page it says it's useful when runway friction is less than ideal. When this technique is in use, the main wing is at a high AoA so the lift it generates will compromise runway friction by a lot. To make wheel brakes anywhere effective, you need the nose down first to reduce the AoA, or pull the nose so high that the wing stalls? – user3528438 May 24 '18 at 00:37
  • Aerodynamic braking with the Vulcan was much more spectacular to watch https://youtu.be/RuqBozAEpDE?t=31s – BDLPPL May 24 '18 at 08:36
  • 1
    One can't mention aero-braking without mentioning the Gripen, who is probably the king of aero-braking with the huge canards and elevons deflected and speed-breaks extended: https://i.pinimg.com/originals/dc/bf/2f/dcbf2f13eb2991460e6eec27164d727c.jpg – DeepSpace May 24 '18 at 09:57

2 Answers2

9

The aero brake in this picture is the chute! and yes, it works!

Your wiki source is mistaken in stating that this use of elevator increases load on the main gear. The wing angle of attack will increase wing lift in multiples of the tail download, as you observe in the extended gear struts.

Landing like this allows the aircraft to slow with less use of brakes. It is counter-intuitive to claim to both save brakes and increase main gear load, which is intended to allow greater use of brakes.

Military jets land at comparatively high speeds, making this more useful since aero drag is proportional to speed squared. It may even be more effective at high speed than brakes, saving brake capacity for later in the landing when aero braking becomes less effective. Brake capacity may be limited to keep brakes small and light.

Nose gear does not have brakes and adds negligible friction.

Pilothead
  • 20,096
  • 3
  • 54
  • 98
  • He doesn't appear to even apply the brakes until about :06 into the video, and judging from the crazy amount of heat and smoke coming off them I would guess the brakes are not too robust. They probably want to get as slow as possible before they even hit the brakes – TomMcW May 24 '18 at 00:12
  • 2
    @TomMcW It's obscured, but I think the smoke you see is the nose wheel touching down. The heat waves are from the jet exhaust; you don't see them behind the left wheel. – Pilothead May 24 '18 at 00:20
  • @Pilothead It might be the angle, but those heat plumes look like they're coming from ahead of the engine outlet. – TomMcW May 24 '18 at 00:25
  • @TomMcW I think it's the angle. You are looking almost right up the tailpipe. The video quality isn't that good either. – Pilothead May 24 '18 at 00:37
6

Actually one can simply apply braking pressure to slow a fighter down. One problem, especially so with early jet fighters, was that they often had very small tires and brakes on the main gear which were inadequate to slow the airplane from touchdown speed to a standstill in a short distance. A good example was the Northrop T-38, which could takeoff in less than 3000 feet of runway but needed over 7000 feet to land on due to the small brakes.

Modern fighter do use aerodynamic braking at airports with long runways, in general to reduce wear and tear on the brakes. Touching down at 160 kts, thence maintaining elevator pressure to hold a 10° or so AoA until the jet’s speed bleeds down to 100 kts or so reduces the jet’s energy state to nearly a quarter of what it was when it touched down, leaving far less work for the brakes to do.

Romeo_4808N
  • 73,674
  • 7
  • 150
  • 274
  • 1
    Do you have a source confirming this 7000' landing distance? I tried looking for one, even for the comparable F-5. What I found was for the F-86 (website requires Flash), and it's comparable to the takeoff run. And F-86 pilots sure loved open-canopy aerodynamic braking even with its airbrakes out :) –  May 25 '18 at 20:26
  • 1
    It’s mentioned here. http://www.warbirdalley.com/articles/t38pr.htm. The other source I have is a friend of mine and a former USAF T-38 IP with over 3800 hours in the airplane who confirmed this. – Romeo_4808N May 26 '18 at 04:48