Fly a P51 Mustang?

Very edifying, thanks. I should try to find these references.

Corky Scott wrote:
On Wed, 04 May 2005 16:30:56 -0600, RomeoMike
wrote:

Corky Scott wrote:

Much great stuff snipped

When the model D Mustang was initially introduced, pilots complained
about it being more unstable than the B. That was because the
fuselage had been cut down and a bubble canopy installed instead of
the earlier turtledeck. This changed fuselage actually diminished top
speed somewhat and caused some instability. The engineers then added
the dorsal fin to the front of the rudder which is now considered one
of the signal visual characteristics of the model D.

Corky Scott


Hi Corky,

Excellent post. I used to believe the above:

that the dorsal fin was added to the D model only, and it was because the
fuselage was cut down. that's what all the books said.

However recent reading of some T.O.'s issued at the time show this may
actually not be the case:

Several crash reports tell of P-51B's and C's crashing because the
horizontal stab was torn off during maneuvering. The report says:

"Unless a dorsal fin is installed on the P-51B, P-51C, and P-51D airplanes,
a snap roll may result when attempting a slow roll. The horizontal
stabilizer will not withstand the effects of a Snap Roll. To prevent
recurrence the stabilizer should be reinforced in accordance with T.O.
01-60J-18 dated 8 April 1944 and a dorsal fin should be installed. Dorsal
fin kits are being made available to overseas activities"

A previous entry for another crash:

Sections II and III of T.O. 01-60J-18 had not been accomplished. The
stabilizer was approximately 20 percent below the strength of a completely
reinforced stabilizer. It is believed that this type of failure will be
completely eliminated after compliance with T.O 01-60J-18 and the
installation of a Dorsal Fin and reverse rudder bost tab."

A Supplement to Basic Technical Order (From old Hap himself) says:

"1. Due to horizontal stabilizer failures which are believed to have
resulted form slow rolls, all P-51B, P-51C an dP-51D airplanes wil not
perfomr slow rolls pending the installation of dorsal fin and rudder
reverse trim tab, and compliance with T.O. No. 01-60J-18."

Part of this T.O. 01-60J-18, it seems, was to "...use 1/4" rivets rather
than 3/16" to attach the elevator outboard and rudder upper hinge fittings,
....to stabilizer ribs, providing additonal shear strength....."

The date of 01-60J-18 is 15 January 1945. By that time maybe most production
51's were D's (Don't know that for sure), so it would SEEM as if the Dorsal
was added for the D's only.

Also, I guess that drillingout the rivet holes to take the larger rivets
didn't weaken the riveted pieces any - they must have had enough meat left
over.


Also you can see photos of P-51B's or C's with the dorsal fin:

http://www.mustangsmustangs.net/p-51...tary/eto/6.jpg

http://images.google.com/imgres?imgu...% 3D%26sa%3DN
Scroll down til you see photos of T9 CK

--
Saville

Replicas of 15th-19th century nautical navigational instruments:

http://home.comcast.net/~saville/backstaffhome.html

Restoration of my 82 year old Herreshoff S-Boat sailboat:

http://home.comcast.net/~saville/SBOATrestore.htm

Steambending FAQ with photos:

http://home.comcast.net/~saville/Steambend.htm

Sorry my mistake. the T.O. 01-60J-18 was dated 8 April 1944

Gregg

--
Saville

Replicas of 15th-19th century nautical navigational instruments:

http://home.comcast.net/~saville/backstaffhome.html

Restoration of my 82 year old Herreshoff S-Boat sailboat:

http://home.comcast.net/~saville/SBOATrestore.htm

Steambending FAQ with photos:

http://home.comcast.net/~saville/Steambend.htm

On Thu, 5 May 2005 16:36:44 -0400, "Morgans"
wrote:

Can you describe the design and placement of these bob weights, and how they
added to stability?

Here's an explanation of a bob weight from a website on supplemental
flight controls:
http://142.26.194.131/aerodynamics1/controls/Page3.html

"Bob weights are sometimes known as counter weights. Their purpose is
to change the amount of control force required to deflect the control
column under different g-loadings.

Normally the amount of force the pilot must apply to the control
column, assuming reversible controls, varies with airspeed only.
However, by installing a bob weight the aeronautical engineer can make
it more difficult to pull on the control column as g-force increases.

The purpose of the bob weight is to reduce the likely hood the pilot
will overstress the aircraft."

I should mention that this explanation comes from a website describing
light airplanes, not fighters. If bob weights can be used to increase
the force necessary to move the elevator as G force increases, they
can also be used to lighten the elevator as G force increases. This
appears to be the intent when used in the P-47 to assist it from
pulling out of high speed dives where the elevator was locked. I
don't think this would be very effective though as the elevator was
locked by the onset of compressibility and the pilot literally could
not move the stick back at all at that point, at least not at high
altitude. Since the nose would not come up, there would be no G force
to work on the bob weight. And yes, this was for sure a problem in
combat. Several times the Thunderbolts dived down on unsuspecting
German fighters from high altitude only to find themselves unable to
pull out of the dive and rocketed by the very startled Germans. At
lower altitude because the speed of sound was faster than a high
altitude, the effects of compressibility lessened and the pilots could
pull out, albeit slowly. The P-38 which also was affected by high
speed elevator locking was actually plackarded against exceeding a
certain speed. Unfortunately that meant that they really couldn't
dive much from high altitude. I've read that the Germans figured this
out and exploited the situation against P-38's but this seems pretty
unlikely to me.

It would appear that bob weights work only with the elevator.

So having a counterweighted control stick (bob weights) could add
pressure to the control stick making it require more force to pull it
back. This is a stabilizing effect and would counter over controling
when the Mustang's rear 75 gallon fuel tank was filled.

Corky Scott

Corky Scott wrote:

I've read that the Germans figured this
out and exploited the situation against P-38's but this seems pretty
unlikely to me.

The standard defensive maneuver used by 109 pilots at that point in the war was
a split-ess or bump over into a dive. They didn't have to change a thing against
the Lightnings. They were forced to use other tactics against the P-47 -- it
could stay with them in a dive and didn't have the temporary power loss problem
that British aircraft had initiating a dive.

George Patterson
There's plenty of room for all of God's creatures. Right next to the
mashed potatoes.

On Fri, 06 May 2005 16:30:22 GMT, George Patterson
wrote:

The standard defensive maneuver used by 109 pilots at that point in the war was
a split-ess or bump over into a dive. They didn't have to change a thing against
the Lightnings. They were forced to use other tactics against the P-47 -- it
could stay with them in a dive and didn't have the temporary power loss problem
that British aircraft had initiating a dive.

That diving difficulty the Spitfires and Hurricane's had existed only
during the Battle of Britain. After that British engineers devised a
method of negating the engine cutting out from starvation from pushing
the nose down suddenly to follow a Messerschmitt doing the same thing
(the British called the maneuver a "bunt"). They installed a sheet of
metal across the top of the carburetor's float chamber that had an
orifice drilled in it. In effect, it was like a fuel tanks baffle
that prevents the fuel from ramming from one side to the other when
the wing's are banked.

With this plate/orifice installed, enough fuel remained over the jets
during this beyond zero G maneuver to keep the engine running.

Me 109's could still dive away from Spitfires anyway though, because
the Spitfire had a higher wing loading and simply could not keep up in
the dive.

But you're right, the Me 109 pilots had to come up with something else
to escape the P-47's, nothing outdove them.

Corky Scott

On Fri, 06 May 2005 13:01:20 -0400, Corky Scott
wrote:

Me 109's could still dive away from Spitfires anyway though, because
the Spitfire had a higher wing loading and simply could not keep up in
the dive.

My apologies, I meant to write that the Spitfire had a lower
wingloading than the Me 109.

Corky Scott

Corky Scott wrote:

On Fri, 06 May 2005 16:30:22 GMT, George Patterson
wrote:


That diving difficulty the Spitfires and Hurricane's had existed only
during the Battle of Britain. After that British engineers devised a
method of negating the engine cutting out from starvation from pushing
the nose down suddenly to follow a Messerschmitt doing the same thing
(the British called the maneuver a "bunt"). They installed a sheet of
metal across the top of the carburetor's float chamber that had an
orifice drilled in it. In effect, it was like a fuel tanks baffle
that prevents the fuel from ramming from one side to the other when
the wing's are banked.

With this plate/orifice installed, enough fuel remained over the jets
during this beyond zero G maneuver to keep the engine running.

Corky Scott

Hi Corcky,

I have the paper here, somewhere, that describes the problem and the fix -
which is more or less as you describe.

What I wonder is:

Was this fix proagated through to the Packard Merlins, for the life of
production? Or were Mustang and later Spitfire Merlins fitted with some
other solution which also solved the problem?

thanks

--
Saville

Replicas of 15th-19th century nautical navigational instruments:

http://home.comcast.net/~saville/backstaffhome.html

Restoration of my 82 year old Herreshoff S-Boat sailboat:

http://home.comcast.net/~saville/SBOATrestore.htm

Steambending FAQ with photos:

http://home.comcast.net/~saville/Steambend.htm

"Corky Scott" wrote in message ...
On Fri, 06 May 2005 13:01:20 -0400, Corky Scott
wrote:

Me 109's could still dive away from Spitfires anyway though, because
the Spitfire had a higher wing loading and simply could not keep up in
the dive.

My apologies, I meant to write that the Spitfire had a lower
wingloading than the Me 109.

Corky Scott

Thanks, that one got me...

You guys are amazing...Thanks for the great history lesson Corky and Gregg