Newsgroups: sci.aeronautics
From: drela@athena.mit.edu (Mark Drela)
Subject: Re: Automatic, pressure regulated slats?
Date: Wed, 1 May 1996 04:35:24 GMT

In article <rddDqJ3B3.Bzn@netcom.com>, jonesbr@cartoon.ecn.purdue.edu
(Brian R. Jones) writes:

|> I have heard allusions to automatic, pressure regulated leading edge
|> slats for light (general aviation) aircraft, but have been unable to
|> find any written documentation on such devices.  I am using the term
|> "automatic" to indicate that there are no hydraulic or electric
|> actuators that control the degree to which the slat is extended.
|> 
|> >From what I understand, the slat extends automatically, based on the
|> pressure distribution over the leading edge of the wing.  Do these
|> devices actually exist or was I witness to someone's wishful thinking?
|> Any leads on conceptual discussions, technical data and/or schematics
|> would be very much appreciated!

The Me-109 German fighter had these.  I'm not aware of any other plane
that has them.

These devices made sense on a fighter, since they would automatically
deploy during a high-G combat turn, say.  The last thing the pilot
wants to worry about at that time is manually deploying high-lift
devices!  These things clearly gave a CLmax advantage to the Me-109.
It had a much higher wing loading than the slat-less Spitfire, but
still had a comparable turn radius.

I don't think the automatic aero-deployed slat makes a lot of sense on
a civil aircraft. The pilot is not under combat pressure, and there is
the risk of the mechanism jamming due to ice or whatever.  This would
be disasterous on landing.

  Mark Drela                          First Law of Aviation:
  MIT Aero & Astro          "Takeoff is optional, landing is compulsory"

From: Charles.K.Scott@dartmouth.edu (Charles K. Scott)
Newsgroups: rec.aviation.military
Subject: Me 109
Date: 27 Jan 1997 15:53:39 GMT

Just finished Leonard K. Carson's book "Pursue and Destroy" which is
mostly about the P-51 and also about his career flying it.  I got the
tip tip from this group by the way.

In the last part of the book, Carson compares German fighters to the
P-51.  He got to fly them both so he's speaking from direct experience,
not conjecture. 

His first comment is that the Messerschmitt is terribly cramped and
lacks any IFR instruments.  It also has very little fuel tankage and
was limited to about 55 minutes flight time at combat power.  This give
precious little time to engage in actual combat.  

He also mentioned that the canopy was very heavy, weighing 50 lbs
because it incorporated a bullet proof window behind the pilots head as
well as a piece of armor.  All this had to be lifted when you wanted to
get out.  This is why, when pilots needed to bail out, they flipped the
airplane inverted and just dropped out; it was too much trouble to
fight with the canopy while trying to save your life.  Visibility out
of the cockpit, he termed atrocious.

As to the flight characteristics, he didn't like the airplane and could
not believe so many expert pilots seemed to prefer it when they could
have flown a Focke-Wulf 190.  Take off could be treacherous if you did
not let the airplane fly itself off the runway.  Controls were
relatively well harmonized at speeds around 200 mph but got very heavy
at higher speeds.  So heavy did the ailerons become at 350 to 400 mph
that it took four seconds to achieve a 45° bank at those speeds.  This,
he termed, was unacceptable.  Part of the problem was the stick
geometry (it was short so only a small leverage could be applied) and
also it had limited travel which meant that it had poor mechanical
advantage.  Also, because the cockpit was so small and cramped, the
pilot literally could not put all his weight behind the stick if he
wanted to.

There were no rudder or aileron trim tabs and the rudder NEEDED one. 
At high speed, a significant amount of left rudder was required to
center the ball or the airplane would fly sideways which of course
affected aim.  During an extended highspeed flight, the pilot could
become significantly fatigued from the need to apply continuous left
rudder.  Consequently at high speed, the 109 could be turned quicker to
the right than to the left.  Now you know why; the right leg was less
tired.

At high speed the elevator trim had to be applied or the airplane
became very nose heavy.  Also, the elevators got so heavy at high speed
that the pilot literally could not pull significant G's which of course
limited it's maneuverability.

The prop was a variable speed unit but NOT automatic like the allies
had.  It was a lever controled prop with a guage indicating where the
pitch was.  The prop was capable of significant pitch changes but the
pilot had to make them.  In contrast, the Allied pilots had a constant
speed prop, they simply set power and let the prop take care of itself.
 They did not care nor did they want to be bothered by what rpm the
prop was maintaining while sweating out a combat situation.

Aerodynamically, the Me 109 was very dirty with a significantly higher
drag coefficient than it's counterparts the P-51 and Spitfire.

Other allied pilots who flew the Messerschmitt commented on how
directionally unstable the airplane was requiring constant course
corrections to maintain flight direction.  This is not uncommon in WWII
fighters as a certain amount of instability assists the pilot in
directional changes which are necessary for combat maneuvering.

About the best thing that could be said for the Messerschmitt was it's
engine, which of course was something W. Messerschmitt did not design.

The Me 109 took a lot of training in order to fly effectively and
needed a lot of pilot attention during high speed maneuvering which
likely is the reason most Luftwaffer pilots engaged in single high
speed attacks and then dove or climbed away.  It also explains why
almost any allied fighter could turn inside the 109, especially at high
speeds.

Corky Scott

From: Charles.K.Scott@dartmouth.edu (Charles K. Scott)
Newsgroups: rec.aviation.military
Subject: Re: Me/109, Bf109 used what engines?
Date: 9 Oct 1997 13:59:56 GMT

In article <343C3C32.D20E0DA0@ix.netcom.com>
Bill Finch <alioth@ix.netcom.com> writes:

> As I recall the Me109 used one engine during WWII and another later in
> Spain. What were they? Also, a friend who flew P-51's in WWII had a
> chance to fly a wartime Me109 in 1944. He said it was difficult to fly
> compared to the P-51. Have any of you flown a real Me109? What's it
> like?

Read the book:



  - 16 -
             Author: Carson, Leonard C.; Hodges, Ken Illustrator
                Title: Pursue & Destroy
          Subjects: WORLD WAR, 1939-1945-AERIAL OPERATIONS, AMERICAN
WORLD WAR,
                          1939-1945-PERSONAL NARRATIVES, AMERICAN
                   New to BIP: 1980/01
           Pub. Date: 071978
                           Price: Cloth Text $19.95 (Retail Price)
                            ISBN: 0-913194-05-0
                     Publisher: Sentry
                         Status: Active Record
                           Notes: Illustrated

In it Carson describes what flying the Me 109 is like, as well as what
it was like flying other German aircraft, he flew a number of them.

He said that the 109 was a mostly manually operated aircraft with the
prop needing to be reset for proper rpm every time you adjusted the
throttle.  This makes for a high cockpit workload for the pilot.  Also,
the rudder did not have a trim tab and the airplane flew at an ever
increasing yaw, the faster it went, which naturally needed to be
corrected by pushing on the rudder bar.  After a flight of an hour or
so, the pilot's leg would get pretty tired pushing on that rudder bar
all the time.  Carson felt that this was why the Me 109 appeared to
break faster to one side than the other when attacked.  He thought that
they could turn quicker to the non tired leg side because that leg
could push harder and faster on the rudder.

He also noted that the canopy included some 30 lbs of head armor which
had to be lifted when you raised the canopy.  This, he surmised, was
why most pilot bailing out of the 109, flipped it inverted and allowed
gravity to pop the hood open.

He didn't like how cramped the cockpit was nor did he like how little
could actually be seen out of the tiny canopy.

All in all he thought the 109 a terrible tool to be fighting in and had
nothing but great admiration for those who not only fought in it but
managed to be so effective.

Corky Scott