Low approaches in ground effect

John Sinclair wrote in message ...
Bill,
If memory serves me right the 4360 had 4 rows of 9
cylinders for a total of 36 jugs. The aft rows were
spiraled to allow cooling to the rear rows, but even
so, the fourth row would run hotter. (KC-97F --circa
1952)
What was the configuration of the 7755?

http://www.enginehistory.org/NASM/Ly...%20XR-7755.jpg
-Dan



At 13:48 19 October 2004, Bill
Lycoming engineers were confident that the R-7755 could
be developed to
produce 10,000 HP.

The R-7755 had nine 4-cylinder inline water cooled blocks arranged around a
crankcase with a 4 throw crank. The liquid cooled radial was intended for
the pusher configurations of the B-35 and B-36. Engines intended for these
aircraft had an integral contra-rotating propeller gearbox in the nose case.
This is the configuration of the XR-7755 on display at the Air and Space
Museum.

The HK-1 was a tractor installation but liquid cooling would still have been
useful, particularly at high power settings used for water takeoff. Engines
for the HK-1 were to be single rotation.

These were VERY advanced engines with overhead cams, 4 valves/cyl, variable
valve timing and would eventually have had turbo-compounding.

Only the B-36 went on to production but with the 4360's it was so
underpowered that 4 jet engines were added. Had it used the R7755's no jets
would have been needed. Convair didn't design the B-36 to be underpowered,
they were forced to use the Pratt. Even so, I fondly remember the
earthshaking B-flat drone of a B-36.

The most interesting of these giants was the radar stealthy Northrop B-35
flying wing. This was the propeller version that was succeeded by the jet
B-49. With 40,000 HP, the B-35 would have been the fastest, longest range
prop bomber of all time even considering the turboprop TU95 Bear. It could
have carried more then 50,000 pounds of bombs to Europe and returned to
bases in North America. But, like Convair, Northrop was forced to use the
P&W 4360.

The cover story that the B35/B49 were cancelled because of "directional
instability" that made precision bombing impossible was nonsense. Just how
accurate do you have to be with a nuclear weapon? The real reason was that
the nuclear weapons of the time wouldn't fit in the Northrop's bomb bays.
Canceling the bomber for that reason would have tipped the Soviets to the
size of US weapons. Size and weight of nuclear bombs was top secret since
the first generation of ICBMs were then under development. The Northrop
flying wings were dead stable about all axes.

The history makes you appreciate the guts of the Smithsonian to put the
XR-7755 on display at all.

Bill Daniels

"John Sinclair" wrote in message
...
Bill,
If memory serves me right the 4360 had 4 rows of 9
cylinders for a total of 36 jugs. The aft rows were
spiraled to allow cooling to the rear rows, but even
so, the fourth row would run hotter. (KC-97F --circa
1952)
What was the configuration of the 7755?



At 13:48 19 October 2004, Bill
Lycoming engineers were confident that the R-7755 could
be developed to
produce 10,000 HP.

On Tue, 19 Oct 2004 21:50:52 GMT, "Bill Daniels"
wrote:


The history makes you appreciate the guts of the Smithsonian to put the
XR-7755 on display at all.

After the crow they had to eat on the Wright/Langley affair, I imagine
they had no intention of colluding in any more coverups.

rj

Uh-Oh!


We've just discovered this winter's discussion topic.
For what it's worth, Gale Craig, a physicist in Anderson,
IN, has written a book titled, I believe, Why Airplanes
Fly, in which he analyzes ground effect. He derives
his theories from Newton rather than from Bernouilli.
It is an interesting read.

A second edition had the title changed to something
like, Don't Abuse Bernouilli. The book is published
privately and has been reviewed on the web. I can
supply an address and telephone number to anyone interested.


At 11:06 19 October 2004, Gerhard Wesp wrote:
nafod40 wrote:
Interesting observation. Flying in ground effect places
the center of
pressure of the wing at about mid-chord, while out
of ground effect the

Are you sure? Note that a forward CG implies a pitch
down moment which
would have to be compensated by negative lift on the
tail. Hence
performance degradtation, contrary to what ground effect
is supposed to
create.

I'm still searching for a good explanation of ground
effect :-)

Cheers
-Gerhard
--
Gerhard Wesp o o Tel.: +41 (0)
43 5347636
Bachtobelstrasse 56 | http://www.cosy.sbg.ac.at/~gwesp
/
CH-8045 Zuerich \_/ See homepage for
email address!

I was flying a Ka 7 in a very strong wind condition. At stall speed up wind
it appeard to have no forward ground speed. At 900ft above ground i started
my circuit and at about 700 ft on downwind i passed the start of the runway
and did a base and finals in a slow turn. At finals i looked down to the
start of the runway at about 45degrees. The wind blow me past the runway
(downwind) aprox 300 meters. I realized that i would not make it back at my
rate of decent and forward motion.Before me was nowhere to land as it was
only threes . I decided to change my alltitude for speed and out of the
headwind and into ground effect. The last few moment was nailbiting as i had
to get over 2 fences and a road but made it. My point: If there is no
headwind it will be better to approach at beast glide angle as ground effect
will be slightly cancelled by profile drag due to higer speed. If you have a
strong head wind it will help to get out of the wind and use ground affect.

Regards

Andre

"CV" wrote in message
...

First a disclaimer: I understand the security issues involved
in the following and would not encourage anyone to try this
at home, but I am interested in the theoretical side of it.

Imagine you get things wrong and are caught out low on final,
still a fair distance out, and it looks marginal whether you
are going to reach the runway or not.

One technique I have sometimes heard described is to dive for
the deck and complete the remaining distance in ground effect.
For the sake of the argument we can assume fairly flat ground,
free of obstacles, though not necessarily landable.

The advantages claimed are usually better glide performance in
ground effect and less headwind and absence of downdrafts close
to the ground.

On the other hand you'll be travelling at higher than optimal
airspeed for most of the distance.

I am wondering how much truth there actually is to this
technique. Would it significantly increase your range and
improve your chances of reaching the field or not ?

Would it perhaps work better against a strong wind gradient
(as I suspect it might), and maybe not help a lot in calm
conditions ?

I'd be interested in any hard data/analysis or otherwise
enlightening comments on this.

Please note though, that I am not talking about high-speed
competition finishes, rounded off with a beatup and a sharp
pullup and all the dangers and other issues involved in that.

Cheers CV