Which way is forward?

[McColm]

Hello,
Prop engines have been installed at the front of an aircraft at the rear, on the wings, over the wings, under the wings and on pylons.
Jet engines either need an air intake at the front, underneath the fuselage; on top or at the side of the fuselage. Or placed on a pylon hung above or below or at the rear of the aircraft.
Nuclear power, yes there have been a few of these. Solar, diesel, parafin, av gas, petrol and coal (gas) have all been used as a fuel, plus a few others.
But I know of only one jet aircraft that can move backwards whilst inflight-The Harrier jump jet.
Which got me thinking, has anyone ever tried to mount a jet engine backwards on a aircraft?
I mean you can buy a ticket for a seat on a train, with your back to the engine. The locomotive will still move forwards or backwards, doesn't matter which end  it is.
You can be a passenger on a VC-10. In a car although it is not recommended to drive for long distances in reverse and if the drivers' seat was turned around he would be going forwards right?.

[pyro-manic]

There are some turboprops where the turbine is mounted "backwards".

[martinbayer]

Can't think of any actually flown jet aircraft with a reverse engine installation, but there were a few V/STOL concepts based on such an arrangement:

http://www.secretprojects.co.uk/forum/index.php/topic,238.0.html

http://www.flickr.com/photos/cutangus/3427834779/

http://www.flickr.com/photos/cutangus/3427834781/

http://www.flickr.com/photos/cutangus/3427834775/in/photostream/

http://www.secretprojects.co.uk/forum/index.php/topic,1525.0/highlight,flying+pig.html

Martin

[McColm]

Thanks for the replies

[kitnut617]

I believe the Bristol Proteus tuboprop engine was a "reverse flow" type.
The air actually enters at the rear of the combustor cans, and then follows the reverse path back out the engine through the turbine. I don't think you could install it "in reverse" though



Duncan

So did the Python Duncan, and the PT6 does too

[kitnut617]

But I know of only one jet aircraft that can fly backwards inflight-The Harrier jump jet.

Technically speaking, it doesn't ""fly"" backwards as the wing doesn't contribute any lift what so ever when moving backwards, the whole operation depending on the thrust of the engine jet blast.

[McColm]

Would the term 'move' backwards in flight, be correct?

[kitnut617]

probably --- 

but I'm trying to understand what you're wanting to do. An aircraft wing will only work in one direction, going forward.  It can fly upside down but still going forward.  I don't think I've ever heard of an aircraft ""flying"" backwards as the airfoil doesn't work that way (someone is bound to correct me now, that's for sure  )

[McColm]

Well,
Let's say that you are flying your P-3 Orion or CP-140 or Atlantique on a ASW mission. The M.A.D. operator spots something on his chart, rather than having to turn the whole aircraft around and letting the sub know above him. Just put it in reverse and go back over the target whilst flying at 150ft, sonorbouys would be released and if it was a threat a harpoon or torpedo released.
Other uses would be bombing-air support of ground troops. Identifying them first before attack, cuts down on blue-on-blue.
In-flight refueling. Tanker can come to you, if you are on bingo fuel. Recon, the possibilities are endless.
And if you had a fighter that could change direction in a dogfight.

[kitnut617]

I get the feeling you don't know how airfoils work McColm,  but most aircraft have a minimum forward speed that will keep them in the air. For a P-3, I think that is about 90 mph but it could be as much as 110-120 mph.  If it were to do as what you're suggesting I don't see how it can possible work.  To put anything into reverse the forward speed has to come to a full stop, even for a split second and all the lift of an airfoil would have long gone way before it ever came to that.  At 150 ft the aircraft would drop straight into the drink.  An aircraft the size of a P-3 when it stalls (that mean's no lift under the airfoil) needs probably 5000 feet to recover and it's probably much more than that.  As I've said in the other post, an airfoil needs forward speed to create lift. No forward speed means no air over the wing, means aircraft no fly ---period.

[Hobbes]

Considering how much energy would be involved in coming to a stop, then reversing; a turn would be quicker and more efficient.

In the CAS scenario: stopping above a battlefield is asking to be shot at. Sitting duck etc. For the same reason you don't fly over the same position twice: after the first time the enemy will be expecting you.

[kitnut617]

But having said all that there are aircraft that can fly very slowly, any light observation aircraft can probably doddle along at around 30-40 mph.  The Flying Pancake is said to be able to get airbourne at 25-28 mph, all it had to do was sit facing the wind and if the wind speed was more than that it would take off.  But is still needs air to flow over the wing which is either created with forward speed or wind travelling fast enough to create an impression of forward speed.

[deathjester]

Try googling GFS Projects - you'll like that!

[rickshaw]

I am disappointed in all of you.  This is a "What if" forum, devoted to "what if" and you quibble about a little thing like which way an aerofoil works?   Such a lack of imagination.   Tsk, tsk, tsk....   

[pyro-manic]

Just need someone to crack zero-point energy, and who can break the laws of inertia, and we'll be sorted.