Vertical Takeoff, vertical Land, aircraft

**skier842** · 12 Aug 11,, 00:25

Having been a aircraft maintenance commander (F-16s) I still have concerns about the practicality of a vertical take off and landing fighter aircraft considering all the logistics involved with refueling, rearming etc, of a fighter aircraft. Not to mention the need for a clean landing/take off secure forward area.

George

**Chogy** · 12 Aug 11,, 14:44

How is the logistics and infrastructure any different from a squadron of helicopters? The VTOL jet might be a bit more sensitive to FOD than the helicopter, but otherwise, they both require fuel and maintenance, and a clear landing area. In the invasion of Iraq, fast-moving logistics units kept both helicopters and M1 tanks well-supplied with jet fuel and ordnance.

It's certainly not insurmountable.

**ace009** · 14 Aug 11,, 14:11

Are there any new VTOL aircraft being produced? Once the Harriers retire I thought all VTOL aircraft will be gone. The F-35B is a SVOTL if I am not mistaken.

**oscar156** · 14 Aug 11,, 19:21

I believe the Russian Yakovlev Yak-38 is still around. And also the V-22 is VTOL.

**Doktor** · 14 Aug 11,, 20:30

Wasn't Yak-38 retired when the SU collapsed?

**omon** · 14 Aug 11,, 22:05

yea, even its successor yak141 was canceled as well, in 1991

**ace009** · 15 Aug 11,, 00:30

Originally Posted by oscar156

I believe the Russian Yakovlev Yak-38 is still around. And also the V-22 is VTOL.

V-22 "Osprey" is not a real VTOL jet aircraft - it is a twin engine tilt-rotor aircraft - which operates more like a helicopter. I always think of it as a "mule" - hybrid of an aircraft and a helicopter.

**Chogy** · 15 Aug 11,, 14:18

While the F-35 is labeled STOVL, one would think that with a restricted load, it could take off vertically. Is this not accurate?

**omon** · 15 Aug 11,, 18:10

good question, you can take all weapons off, but you still need fuel, and vto burns a lot of it, landing almost empty is different, can't take off almost empty, that is my take on it anyway, might not be correct.

**ace009** · 15 Aug 11,, 18:40

Originally Posted by omon

good question, you can take all weapons off, but you still need fuel, and vto burns a lot of it, landing almost empty is different, can't take off almost empty, that is my take on it anyway, might not be correct.

I think there is one more minor difference between VTO and VL - for take off you are working AGAINST gravity, while for landing, you are working with it. For take off, the engines have to lift the whole weight of the aircraft, while for landing, the engines are only reducing the downward speed to an acceptable momentum for the landing gear. My guess is the VTO will require almost twice as much engine power as VL ...

**Chogy** · 17 Aug 11,, 14:17

Remember that a gas turbine engine, regardless of whether it is on a VTOL aircraft or a normal one, is usually at 80% or greater the entire time it's airborne. It's not like enormous amounts of fuel are consumed in a vertical maneuver... the engine is at 95% to 100%, just as it'd be for a rolling takeoff. Plus, the F-35 STOVL uses a lift fan and PTO shaft for the bulk of its lift, not redirected exhaust, and this is much more efficient than swiveling nozzles like a Harrier.

I can't see any reason the F-35 couldn't take off vertically at reduced weight. For a counter-air mission, loaded only with AA missiles, it should do fine.

**Stitch** · 17 Aug 11,, 16:42

Originally Posted by Chogy

Remember that a gas turbine engine, regardless of whether it is on a VTOL aircraft or a normal one, is usually at 80% or greater the entire time it's airborne.

Chogy - I always wondered about that; what was your typical throttle setting at subsonic cruise speed? I always imagined (having never flown a gas-turbine aircraft) that it wouldn't have to be very high (say, 50%) in an aircraft like the F-15, since the engines were so powerful.

**Chogy** · 18 Aug 11,, 14:06

I guess we should consider fuel flow as more important than, say, N1 rotor percentage, because with a gas turbine, going from 90% N1 to 100% N1 delivers FAR more than 10% additional thrust. It's probably more like 35%.

At a given altitude, if military power is some arbitrary fuel flow, say 8,000 lb/hour, typical combat cruise might be 7,000, and max endurance, just keeping the jet in the air at max L/D, might be 5,500. In a nutshell, the engines remain very close to military power for an entire mission. AB use is another story, and produces insane fuel flows... An F-15 can consume all of its internal fuel in a single dash from mach 1 to mach 2.3

My point with all this is that a VTOL airplane in takeoff will be little different from a normal jet, and landing will consume more fuel, but nothing horrible. An additional 45 seconds to 1 minute at 100% mil power, when most of the 2 hour mission might be at 95 to 100% anyhow. The fuel is not a factor with VTOL, it's weight and lift that matters.

**Gun Grape** · 19 Aug 11,, 00:22

Originally Posted by ace009

Are there any new VTOL aircraft being produced? Once the Harriers retire I thought all VTOL aircraft will be gone. The F-35B is a SVOTL if I am not mistaken.

The Harrier is a STOVL aircraft if you want to carry anything but 2 missiles for self defence Both AV-8 and F-35B are stovl aircraft with limited VTO capability

**junoth1001** · 21 Aug 11,, 16:48

Originally Posted by Gun Grape

The Harrier is a STOVL aircraft if you want to carry anything but 2 missiles for self defence Both AV-8 and F-35B are stovl aircraft with limited VTO capability

The RAF version, the VTOL aspect of the aircraft, were only used in certain operational circumstances and for impressing civilians, otherwise, it took off and landed back conventionally.

When using the VTO option, if armed, the Harrier had to top up from a tanker.