Re: Vertical stabilisers on supersonic fighter aircraft
- From: mkellytx@xxxxxxxxx
- Date: 16 Feb 2006 18:48:15 -0800
CCW N4AOX wrote:
Pardon the top posting:
The F4, F5, F16, F104, F106, F111 have single vertical stabs. but also fly
at or near Mach 2 at high altitudes. How do you explain the difference.?
The F14, F15, F18, F22 have double vertical stabs. and operate in roughly
the same flight regime, do they not?
Good questions. Each airplane mentioned is designed to a different set
of requirements and many do operate close to Mach 2.
The F-4 as originally designed didn't have enough vertical tail surface
to provide the necessary LD stability at high speed and altitude.
Since, many of the design parameters were already set the solution was
to cant the horizontal tail surfaces down. This provided enough of a
vertical component to give the bird the needed stability. This was
actually a case study we looked at in a USAF TPS Equations of Motion
short course I took a while back. Additionally, the Phantom wasn't
well known for its great maneuverability.
The F-5 isn't nearly as fast as the later teen series fighters. IIRC
it only tops out at around 1.6 or so. Additionally, the wings aren't
highly swept and the two engines are small and close to the centerline.
A great big vertical wasn't required for where it flies.
The Viper most certainly augments its vertical area with the ventral
strakes and has a nice sized tail for a single engine jet. The nice
thing about those strakes is that they add stability at high AOA.
Definitely a good thing for a fighter meant to turn and burn.
The Zipper had very small wings with no sweep and a tail a good
distance from the CG. Even then it was speed limited by its stability
as I believe Walt has pointed out (please correct me Walt if I'm
mistaken or if you can better explain). That said, it also had a
ventral fin (the Italian version had two).
The F-106 was fast, but had a delta wing that doesn't have the same bad
behavior as a swept wing ( although it does have its draw backs ).
Still it has a nice sized tail on it.
The F-111 mostly was meant to go low, fast and deliver bombs ( ok shoot
Phoenixes at Backfires for the Navy ). Kurt explained pretty well the
Vark's behavior in his post previously.
The other thing that bears mentioning is that all of those teen series
fighters are the generation following the F-4, F-5, F-104, F-106 and
F-111. The larger verticals, strakes and multiple tails are signs of
lessons learned from the previous generation of aircraft. The F-22 is
supposed to not only cruise, but be maneuverable high, fast and at high
AOA. Hence the two barn doors on top of the aft end of the jet.
After all of the long descriptions the mechanics of how and why are a
set of long, non-linear differential equations that us engineering
types make tons of assumptions to simplify. We do a lot of linearizing
about trim conditions and avoid simulating the full set unless someone
pays us a lot of money ;).
Michael Kelly
BUFF Flight Tester
.
- References:
- Vertical stabilisers on supersonic fighter aircraft
- From: Dermott
- Re: Vertical stabilisers on supersonic fighter aircraft
- From: mkellytx
- Re: Vertical stabilisers on supersonic fighter aircraft
- From: CCW N4AOX
- Vertical stabilisers on supersonic fighter aircraft
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