Any P51 experts out here?

In article t,
"Dudley Henriques" writes:
Thanks much Pete. That's the exact quote I was getting on this, so this
has to be the training manual in question.
I asked around the P51 community a bit on this and have heard back from
Vlado Lenoch and Glenn Wegman. Neither mentioned the manual per se, but
not to my surprise, agreed with me that there are no basic issues in
slipping the 51 save doing it below 200 feet due to the quick and
sometimes unpredictable payoff behavior of the wing at low speed and
high angles of attack.

Thanks. Back when Don Davidson had his Mustang, he told me that he
had no problems at all with anything he wanted to do with it. (I know
- that's a somewhat loaded statement, but he's practice aerobatics
over my house, so it wasn't all straight and level.) The stability
and control derivitives from the NACA documents indicate that there
shouldn't be any problems, either.

When I was told about this being in this manual, I immediately dove into
my dusty old desk and dug out the old dash 1 for my airplane. Under
rudder control, it plainly states that sideslips are no issue at all,
and in fact mentions sideslips by name.
My take on the training manual is that pilots coming out of Advance in
the AT6 and transitioning into 51's during lead in fighter training were
faced with dealing with the laminar characteristics of the Mustang
coming off the comparatively higher lift characteristics of the T6,
which could be slipped like mad. I'm fairly certain, although I could
never prove this, that the Training Command thinking at the time was to
save lives and conserve sheet metal. The Mustang really doesn't need to
be slipped on final due to the extremely high drag of the last flap
position at 50 degrees (47 actually) plus running up the prop to low
pitch against the stops is like dragging your feet in the mud in this
airplane. My guess is that ATC just decided after looking at the log
books for total time of the guys transitioning into the Mustang that
having this restriction saved them a lot of trouble writing accident
reports, since it wasn't necessary to slip the airplane anyway.
The wording is interesting though, and I guess one could stretch a point
in justifying the restriction by noting control response degradation in
the left side of the Mustang's envelope.

That makes a lot of sense, from a Peacetime Air Force point of view.
I've heard similar tales about the F-86. Apparantly the Word Went
Down in ATC that F-86s couldn't be slipped, while pilots all over the
world were slipping them in on final.

About the military/civvie conversions;
Mine had the old radios and junk in it.
The military Mustang had a bunch of crap in it that more or less kept
the cg in limits. When the guys started gutting them and converting
them, they took a lot out and threw the cg forward enough that they
needed weight in the tail or at least had to be REAL careful landing
them. It wasn't uncommon to see full nose up pitch trim on some of them
after 3 pointing them.

To tell you the truth, that seems more than a bit dicey to me. Wasn't
anybody doing Weights & Balances on them? Throwing the CG out to make
room for more stuff sounds like a disaster in the making. Especially
if the pilot's new to the airplane, and new to high performance
airplanes in general.

I always landed the Mustang with some speed on the airplane, tail low on
the mains anyway, but the cg can be a problem for the pilots who like to
do 3 pointers in the airplane.

Oddly enough, the L-19 was the same way for me. I couldn't 3-point
the blasted thing for beans, but a tail-low wheeler was the most
comfortable.

I remember Vlado telling me something about Moonbeam's configuration,
but I forget if he has the cg issue. I would assume he does, as Collins,
Bendix, and King, are a whole lot lighter than that old crap we had in
there :-))
Dudley
I guess the bottom line on what the manual says would be;
Manual says "no slips"
Dash 1 says, "No slip restrictions"
I would say, "no problem at all, but not under 200 feet"
Other P51 pilots are checking in with "I do it"
Puzzling how the government does things isn't it? :-))))

I've seen worse.

--
Pete Stickney

Without data, all you have are opinions

Did the Navy ever have P-51's in its inventory?


"Dudley Henriques" wrote in message
nk.net...
I'm researching something and can use some assistance if anyone has the
expertise or the inclination to be of assistance with this.
Apparently there was a training manual put out during the forties on the
P51 Mustang (not the airplane's dash 1 which totally contridicts this
manual) that said the 51 could NOT hold or maintain a slip.
I'm interested in any information on that manual, and/or the reasons for
this statement.
I already know the Mustang can be slipped as I've slipped it many times.
What I need is origin information on this exact training manual and any
reasoning for the no slip ability statement being in that manual.
Thank you
Dudley Henriques
International Fighter Pilots Fellowship
Commercial Pilot/CFI Retired
for private email; make necessary changes between ( )
dhenriques(at)(delete all this)earthlink(dot)net

Dudley,
Let me start out by saying that I'm not a pilot and have never flown
anything with more power than a T-34A (flown from the backseat with a
"real pilot" up front) and a P-3 from the right seat.
Would the sideslip issue have been affected by the addition of the
fairing forward of the vertical stab? IIRC the P-51B/Cs didn't need the
fairing because of the extra side area they had compared to the
D-model. The early D-models apparently did have directional stability
issues prior to addition of the fairing. Maybe the training manual came
out before it was added?
Don McIntyre
Clarksville, TN

"Don McIntyre" wrote in message
oups.com...
Dudley,
Let me start out by saying that I'm not a pilot and have never flown
anything with more power than a T-34A (flown from the backseat with a
"real pilot" up front) and a P-3 from the right seat.
Would the sideslip issue have been affected by the addition of the
fairing forward of the vertical stab? IIRC the P-51B/Cs didn't need
the
fairing because of the extra side area they had compared to the
D-model. The early D-models apparently did have directional stability
issues prior to addition of the fairing. Maybe the training manual
came
out before it was added?
Don McIntyre
Clarksville, TN

That's an astute observation and is correct about the airplane. The post
block 10 D's did have a dorsal added for improved directional stability.
It's always been my understanding that this was due to airflow issues
coming off the bubble canopy changeover, but I ran into a NA engineer
some time ago who said it was also related to the fuselage tank
installation. I didn't have the fuselage tank in my airplane so that was
never an issue for me anyway.
It's interesting what you have brought up about the training manual.
It's dating is August 45.
Dudley Henriques
International Fighter Pilots Fellowship
Commercial Pilot/CFI Retired
for private email; make necessary changes between ( )
dhenriques(at)(delete all this)earthlink(dot)net

In article ,
"BOB'S YOUR UNCLE" writes:
Did the Navy ever have P-51's in its inventory?

They tested them several times, including a set of Carrier Trials
aboard the U.S.S. Shagri-La (CV-31) in November adn December 1944.

--
Pete Stickney

Without data, all you have are opinions

Dudley,
I don't quite understand how the fuel tank installation relates to
the dorsal fairing. Wasn't the fuel tank related to the "ass-heavy" CG
on the B-model (or did that also apply to the D)? The airflow off the
canopy makes a lot more sense to me.
I'm not trying to pick nits here, just curiousity has reared it's
ugly head. 8-)

Don McIntyre
Clarksville, TN

"Don McIntyre" wrote in message
oups.com...
Dudley,
I don't quite understand how the fuel tank installation relates to
the dorsal fairing. Wasn't the fuel tank related to the "ass-heavy" CG
on the B-model (or did that also apply to the D)? The airflow off the
canopy makes a lot more sense to me.
I'm not trying to pick nits here, just curiousity has reared it's
ugly head. 8-)

I wouldn't disagree with this . Just mentioned it because it was a NA
engineer who threw it out there to us at one time.
In my opinion it was the canopy change that necessitated the need for
the dorsal extension. I remember questioning him at the time as well.
Dudley

Dudley Henriques wrote:
"Don McIntyre" wrote in message
oups.com...

Dudley,
I don't quite understand how the fuel tank installation relates to
the dorsal fairing. Wasn't the fuel tank related to the "ass-heavy" CG
on the B-model (or did that also apply to the D)? The airflow off the
canopy makes a lot more sense to me.
I'm not trying to pick nits here, just curiousity has reared it's
ugly head. 8-)


I wouldn't disagree with this . Just mentioned it because it was a NA
engineer who threw it out there to us at one time.
In my opinion it was the canopy change that necessitated the need for
the dorsal extension. I remember questioning him at the time as well.

It sort of makes sense. The "ass-heavy" rear fuel tank take away
stability, the dorsal fairing contributes to stability. The bubble
canopy upset the airflow behind it and in front of the fin, the
dorsal fairing may have improved this.

So the question is whether the dorsal fairing was added for the first
reason, the second, or both. The airplane may be too old a design to
get a definitive answer, but I wouldn't be surprised if they added
the fairing for both reasons.

In article ,
Jim Carriere writes:
Dudley Henriques wrote:
"Don McIntyre" wrote in message
oups.com...

Dudley,
I don't quite understand how the fuel tank installation relates to
the dorsal fairing. Wasn't the fuel tank related to the "ass-heavy" CG
on the B-model (or did that also apply to the D)? The airflow off the
canopy makes a lot more sense to me.
I'm not trying to pick nits here, just curiousity has reared it's
ugly head. 8-)


I wouldn't disagree with this . Just mentioned it because it was a NA
engineer who threw it out there to us at one time.
In my opinion it was the canopy change that necessitated the need for
the dorsal extension. I remember questioning him at the time as well.

It sort of makes sense. The "ass-heavy" rear fuel tank take away
stability, the dorsal fairing contributes to stability. The bubble
canopy upset the airflow behind it and in front of the fin, the
dorsal fairing may have improved this.

So the question is whether the dorsal fairing was added for the first
reason, the second, or both. The airplane may be too old a design to
get a definitive answer, but I wouldn't be surprised if they added
the fairing for both reasons.

The directional stability of an airplane depends, basically, on where
you put it's side area - area ahead of the CG is destabilizing, and
area behind it adds to the stability. When they cut down the aft
fuselage of the P-51 to put the bubble canopy on hte "D" models, they
lost some ditectional stability. (Yaw) The added the dorsal extention
to the rudder to try to remedy this, and in the later H-models and the
Temco and Cavalier builds put a taller fin on the airplane.

The data for this still exists. Buried in the uncatalogued files on
the NACA Technical Reports Server are the results of the wind tunnel
tests used to determine the H-models fin shape. It's also got the
stock D-model data in the report.

Note that the P-51 wasn't the only airplane theat needed its
directional stability punched up a bit after getting the bubble
canopy. A dorsal fin was added to late model P-47Ds, Ms, and Ns, and
the Spitfire got a brand new fin & rudder.

The fuselage auxilliary tank moved the CG aft, right to, or perhaps a
bit beyond, the practical limit for an aft CG. This had a small
effect of directional stability, but a huge effect on pitch
(longitudinal) stability. The airplane tended to be unstable in
pitch, very, very light on the stick at low Gs (Something like 1.5
lbs/G have been reported) and with a felt force reversal somewhere
around 4 Gs. This led to NAA and the USAAF devising a bobweight
system in the elevator circuit that increased the feel of the airplane
in pitch.

--
Pete Stickney

Without data, all you have are opinions