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View Full Version : Why not "pushers"?



georgeo76
06-30-2004, 04:21 PM
Why do AC designers prefer to place the propeller in the front of the AC?

I mean take the large, multi-engine bombers for example. Doesn't the turbulence created by the props interfere w/ the airfoil?

georgeo76
06-30-2004, 04:21 PM
Why do AC designers prefer to place the propeller in the front of the AC?

I mean take the large, multi-engine bombers for example. Doesn't the turbulence created by the props interfere w/ the airfoil?

Taylortony
06-30-2004, 05:20 PM
A lot is to do with Engine cooling, centre of gravity of the Aircraft and pushing a mass of air over a wing will help produce lift. The likes of the Lancaster had the H tail design to take advantage of the airflow from the engines as the vertical fins are positioned in the Airflow from the inboard Engines and hence gave rudder authority earlier on in the take off run and vise versa on the landing run.

This is a good example of the Centre of Gravity issues, see how far forward on this BAe 146 they have had to hang the engines on the pylons to get the CofG right.
http://www.smiliner.com/pics/n_unitedexpress_n294ue.jpg

ElektroFredrik
06-30-2004, 05:39 PM
I believe in a small plane with the engine
behind the pilot, the engine is very likely
to come forward and smash the pilot in an
otherwise not-so-dangerous half-crash.
Also with pusher-fighters the prop will slice
and dice the pilot if he bails. So you either
have to remove the prop with explosive bolts
or have an ejection seat. That means more work
for the engineers...
just take a look at this SAAB J21
http://www.kgwings.com/j21/j21_05.jpg

As for the big boys, didn't the B-36(?) have
pusher-engines. Also the flying wing bomber
(XB-49?) had pushers. the Do-335 had one pusher
and one puller. If flying on one engine if was
faster on the puller than on the pusher?

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BombTaxi
06-30-2004, 05:57 PM
Pushers did have crash saftety issues. Also, the view to six o'clock is obstructed, and the engine is more exposed, as any rear-qyarter attack (i.e. most fighter passes) are likely to hit it. That was why the RFC abandoned them for the Sopwith Pup in WW1

Dawg-of-death
06-30-2004, 06:03 PM
Cessna (Bat-29) made a puller-pusher for a while ........... forget modle

Bad-MF(Mongrel Fighter) AKA .......Dawg-of-death

Amanda_Hugnkiss
06-30-2004, 06:14 PM
That movie was called BAT-21, by the way. And the Cessna centerline thrust aircraft was the C-337 commonly known as the "Push me Pull you". But it suffered from high temps on the rear engine because it could not get proper cooling. Additionally, you had to start your take off with the rear engine first so you could be certain it was running. The front engine propwash would windmill the rear engine prop and you did not always know the rear engine shut down.

Dawg-of-death
06-30-2004, 07:36 PM
21 . 29 what ever it take LOL..........good book/movie

Bad-MF(Mongrel Fighter) AKA .......Dawg-of-death

Fritzofn
06-30-2004, 09:17 PM
the Jap's had an insane Pushplane, with 7 bladed prop. Kyushu J7W1 Shinden.
I'm unsure of arment proposal but i belive it's eighter 4*12.7 or 20mm guns or a combination.

When u get to HELL, Tell'em I'll sent u.....U'll get a group discount

wayno7777
06-30-2004, 09:23 PM
Cessna Skymaster,can't remember the number right now. http://ubbxforums.ubi.com/images/smiley/35.gif

http://img74.photobucket.com/albums/v224/wayno77/Dux_Wreck.jpg
Any landing you can walk away from is a good one!

WUAF_Badsight
06-30-2004, 10:29 PM
did someone say Shinden ? . . . . . .

.
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WTE_Galway
06-30-2004, 10:36 PM
pushers traditionally have mainly been seaplanes

the most famous contemporary pusher is the starship of course

if you are a beechcraft starship fan there is a great screen saver here:

http://tucows.sympatico.msn.ca/themes/preview/217781.shtml

WUAF_Badsight
06-30-2004, 10:38 PM
http://img7.photobucket.com/albums/v18/Badsight/Shinden.jpg

power : 2130 Hp

top speed : 750 Km/H @ 20,000 feet (projected)

armament : prototype , nothing

armament : prodution planes were not made but the plane was meant to carry four 30mm cannon

http://img5.exs.cx/img5/1456/Shinden_J7W19.jpg

http://img13.exs.cx/img13/8227/Shinden_J7W116.jpg

.
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actual UBI post :
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Jasko76
07-01-2004, 01:02 AM
ElektroFredrik - nice J21A!!

I built one some 8 years ago, it looks just like yours.

Regards,

Jasko
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Zmaj od Bosne

IL2-chuter
07-01-2004, 02:19 AM
The Cessna 336/337 and Do335 (do the numbers seem coincidental?) both flew faster (better all around) on the rear engine. If you could pick an engine to lose, it would be the forward one. CG played a big part in the canards not making it into widespread use. The Shinden was accepted for production in spite of its handling quirks, the same reasons why the US didn't produce any. I've checked out that Shinden (and Assender) and its in poor shape, but there is hope. Someday at Udvar-Hazy . . . http://ubbxforums.ubi.com/images/smiley/16x16_smiley-tongue.gif

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lindyman
07-01-2004, 02:26 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by WTE_Galway:
the most famous contemporary pusher is the starship of course
<HR></BLOCKQUOTE>

Burt Rutan seems to like pushers.

If you have a pulling prop in the nose, the prop wash does interfere with the airfoil, but that is not only a bad thing. There's an advantage too, in that in takeoff acceleration, the airflow over parts of the wings is faster than your airspeed, which shortens the takeoff roll a little bit.
_
/Bjorn.

crazyivan1970
07-01-2004, 02:29 AM
bunch of odd looking birds http://ubbxforums.ubi.com/infopop/emoticons/icon_biggrin.gif

V!
Regards,

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Prof.Wizard
07-01-2004, 02:36 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Fritzofn:
Kyushu J7W1 Shinden.
<HR></BLOCKQUOTE>
http://www.eagle.ca/~harry/aircraft/shinden/shinden4.jpg
http://www.eagle.ca/~harry/aircraft/shinden/

Definitely looks great! http://ubbxforums.ubi.com/images/smiley/93.gif

-----------------------------

Me-163's HWK 109-509 Rocket Engine
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Prof.Wizard
07-01-2004, 02:41 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by IL2-chuter:
The Cessna 336/337 and Do335 (do the numbers seem coincidental?) both flew faster (better all around) on the rear engine. If you could pick an engine to lose, it would be the forward one.<HR></BLOCKQUOTE>

I wish we had the FM of the 'Pfeil' to try flying around only with the rear engine, waiting for the front one to cool down... http://ubbxforums.ubi.com/images/smiley/16x16_smiley-tongue.gif
Hehe, but I think I've read that in real life the rear one on the Antseater had heat issues.

-----------------------------

Me-163's HWK 109-509 Rocket Engine
http://www.mihailidis.com/images/HWK109509.jpg

WUAF_Badsight
07-01-2004, 03:39 AM
AntEater was the trainer 2 seat version

it wasnt the nickname for the fighter as well was it ?

.
__________________________________________________ __________________________
actual UBI post :
"If their is a good server with wonder woman views but historic planesets...let me know!"
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WUAF_Badsight
07-01-2004, 03:44 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by IL2-chuter:
The Shinden was accepted for production in spite of its handling quirks, the same reasons why the US didn't produce any.
<HR></BLOCKQUOTE>

what handeling quirks ?

it only flew twice

for a total of 45 min . . . . the only reports were of takeoff torque & a driveshaft vibration

it wasnt flowen in the US

there were 2 prototype Airframes in a finished state (one didnt have its motor fitted) but only one flew

the one that flew twice is the one that was shipped back to USA

its a static display at the smithsonium still isnt it ?

.
__________________________________________________ __________________________
actual UBI post :
"If their is a good server with wonder woman views but historic planesets...let me know!"
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Skarphol
07-01-2004, 04:18 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Taylortony:
This is a good example of the Centre of Gravity issues, see how far forward on this BAe 146 they have had to hang the engines on the pylons to get the CofG right.
<HR></BLOCKQUOTE>

The placement of engines in front of the wing is not done with the intention of getting the centre of gravity right! That would have been much easier achieved by moving the wing slightly forward.
The reason is that the wing tends to bend upwords during flight. On large aircraft this can make the tip travel more than a meter up. On a straight-winged aircraft this is no problem. On a sweptwinged aircraft, this will mean that the outer portion of the wing gets the airstream slightly on the upper side of the wing, thus eleminating that part of the wings lift. This will lead to the wings centre of lift moving forward, as the tips doesn't produce lift anymore. As the centre of lift moves forward, away from the centre of gravity, the aircraft will tilt slightly nose-up. This will give the wingtips their lift again, as the airstream now hits the wingtips as it was supposed to. This will move the centre of lift back towards the centre of gravity again, and the nose will fall back to normal. This will repeat itself with a frequency that can be calculated thinking of the wing as a steel spring, with a certain inertial frequency. The plane will oscillate in level flight.
To avoid this oscillation the hevy weight of the engines is used as a mass balance to dampen the motions of the wing. AFAIK the engine could be placed behind or forward of the wing, but the uninterrupted airflow of the latter is preferred.

Skarphol

"Trying is the first step towards failure!" Homer Simpson

[This message was edited by Skarphol on Thu July 01 2004 at 04:05 AM.]

Prof.Wizard
07-01-2004, 04:55 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by WUAF_Badsight:
AntEater was the trainer 2 seat version

it wasnt the nickname for the fighter as well was it ?

<HR></BLOCKQUOTE>
No. It was the fighter in general. All versions of Do-335.

-----------------------------

Me-163's HWK 109-509 Rocket Engine
http://www.mihailidis.com/images/HWK109509.jpg

ElektroFredrik
07-01-2004, 05:30 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Jasko76:
ElektroFredrik - nice J21A!!

I built one some 8 years ago, it looks just like yours.
<HR></BLOCKQUOTE>

Sorry, not mine.
I have one but that's a lot uglier. And some
other ugly models. Last time I counted I had
some 30-40 planes collecting dust. All ugly

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