After the vertical thrust, how does it fly foward? Without dropping altitude.

By spinning it's wheels.... :D


Or tilting its jets/ducting. As long as total thrust > plane's weight, you can use any extra thrust to go forwrd until your wings start providing lift.

er...

talking about the Harrier? The jets swivel to slowly transition the vertical thrust into horizontal thrust, then shut off.

And then you drop out of the sky :lol:

well, the VTOL jets turn off, and the main jets take over :lol:

Hah, I just LOLed.

Yes, I stuck the -ed at the end of LOL again. :D

Some days I wish I had VTOL jets on my car.

I'm no VTOL expert, but there are generally three ways they work. They have seperate engines that provide vertical lift, they rotate the engines, or they have nozzle that direct the vector of the thrust. Regardless you aren't going to instantaneously go horizontal and no vertical. They probably start to climb while they move forward until they have enough lift to only have horizontal thrust. That make sense?

As far as I am aware the current "in use" VTOLs, Harrier, and V-22 both use their main engines for both vertical and horizontal flight by means of rotating the engines themselves(V-22), or the ducting(Harrier) behind the engine to redirect thrust.

I think one of the JSF designs had/has an additional lift fan, but the main engines do most of the heavy lifting.

Oh really? I just figured it was a two engine design, but it makes sense to be a single engine because you need a massive amount of vertical thrust to take off vertically. A smaller support fan just wouldn't cut it, would it?

The AV8B Harrier II has 4 rotatable main engine exhaust nozzles that can rotate slightly past 90 degrees, providing thrust for VTOL takeoff, as well as rotating horizontal for conventional flight.

http://www.jettech.ch/Harrier_AV8B.gif

http://rogerritter.com/images/aviati...B/File0006.jpg

There is a single engine feeding all four nozzles, though IIRC hot exhaust exits only the aft nozzles, while the front are cool air from the turbofans.

http://www.harrier.org.uk/history/im...ion_system.jpg

In addition, for yaw/pitch/roll control while hovering, there are reaction thrusters in the nose, tail, and wingtips that can push the plane about while it's balancing on the main nozzle thrust.

http://www.harrier.org.uk/history/im...rol_system.jpg

In addition, the Harrier is an *extremely* difficult plane to fly in hover. The original Harrier had something like a 1/5 fatality rate for the pilot training program. Much has been improved in the Harrier II, though a full fly-by-wire system would probably make the plane much safer yet.

Finally, the Harrier rarely utilizes true vertical take-off. It's much cheaper on fuel to use a short roll-out w/ a 45deg thrust vector. Plus it allows the plane to take off with a much heavier payload. And for the really heavy launches, there's the ski ramp:



/me used to be a big military aircraft nerd.

/considers retracting his wish

That's nuts.

Oh, and Dean... the Joint Strike Fighter is supposed to have a VTOL variant:

http://www.smiths-aerospace.com/imag...TOL%20(RN).jpg

There are competing engine designs. One is just like the Harrier, except with three nozzles, (fore and one aft). The other uses a drive shaft that turns a nose-mounted fan instead of the forward exhause nozzle.

http://www.vtol.org/images/Figure02.jpg

There is a hatch on the back of the plane that opens so that air is pulled into the main engine from above (prevents injesting dust from the regular intakes while in hover).

Yeah, I know VTOL was a design requirment, that's why I mentioned iot. I just couldn't remermber if the seperate lift fan design was the one that won the contract or not. There is actually a really good Discovery channel show on the design competition.

The harrier also has the worst crash record and highest maintenance cost of any naval plane.

Actually, I don't know which one they selected (if they've even got that far). But my money's on the Boeing design that's sans the ducted fan and associated driveshaft/clutch... that's just too many bits to break. Stick w/ what works... the design similar to the Harrier w/ the forward nozzles.

I believe it.

On the same note, I bet it saves the English Navy a buttload of money, since they don't have to have full-size aircraft carriers like we use in order to have a capable naval air-force.

Sorry, Complexity won out, and the Lockheed lift fan won.

One of the primary reasons was it has better resistance to heat soak. (The engine injesting its's own hot exhaust and losing thrust) This is one of the Harrier's biggest problems. Losing thrust in close proximity to the ground in VTOL configuration.

From http://www.jsf.mil

Wow... I figured the dorsal intake would prevent the hot air injestion issue, and that the front nozzles would be cool air anyway.

'Course, I also thought the YF-23 would be picked over the YF-22.

Merits of a design sometimes have little to do with which competitor actually wins in a military design competition.

My lab did some of the background and safety stuff for the JSF. It's crazy the way they make decisions, let me tell you. Or rather not tell you. haha

Lemme guess... you could tell us, but then you'd have to kill us, right?

This thread is informative. Today when some of the other managers were talking about VOTL aircraft I totally laid the fucking smackdown on them.

No, I'd probably just get fired. I dunno what's allowed to be public and what's not, so I wouldn't risk it.

:lol: :lol: :lol: Tyson makes me laugh. I can totally picture 3 or 4 guys staning in the middle of the warehouse floor, or coffee room with Tyson spanking them with his wisdom...

The JSF Fighter competition discussed earlier is on Nova starting in 30 seconds... Channel 5.

Yeah I watched that last night, good show. Good channel that PBS, for the most part.
Who won the contract? I missed the last part.

Just for future reference, I have slides that explain almost every aerospace concept. In case you guys get curious about something.

That was pretty cool...thanks for the heads up Dean. Lockheed won the competition since they were able to do a short runway takeoff, achieve supersonic speed, and land vertically all in one flight...somthing Boeing had yet to achieve. But Boeing is still #1 in the sales of unmaned aircraft, they were saying.

Subsonic airflow accelerates when comes to a constriction. Why does supersonic airflow do the opposite?

Some of the equations got jacked. I'll complain. haha You can look them up on google I guess.