More long-range Spitfires and daylight Bomber Command raids, with added nationalistic abuse (was: #1 Jet of World War II)

In article ,
Guy Alcala writes:
I'll step with some trepidation into Pete's territory here as he explains this
stuff far better than I do, but we've been keeping him busy doing calcs. The high
aspect ratio wing provides good L/D ratios, increasing range performance as well as
lift at low angles of attack. Here's how the a/c's aspect ratios stack up, from
low to high:

Stirling 6.72:1;. B-17, 7.58:1; Halifax (early) 7.81:1; Lancaster 8.02:1; Halifax
(late) 8.51:1; B-24, 11.55:1; B-29, 11.48:1.

As you can see, the B-24, designed a couple of years later than the British heavies
and five years or so after the B-17, has a much higher aspect ratio wing, and the
B-29 follows this practice. The wing area of the B-24 was considerably lower than
the others, for low drag. Good altitude performance requires some combination of
low wing-loading (high wing area for weight), engine thrust, and aspect ratio.

While the B-24 had good engine power at altitude and a high aspect ratio, it also
had high wing-loading compared to its contemporaries (not the B-29). It had better
altitude performance than the British a/c because of its engine supercharging, not
its wings. The B-17, with similar supercharging as the B-24 had a higher combat
and service ceiling, because although it had a moderate aspect ratio wing it also
had far lower wing-loading, and was able to fly slower. The B-24 cruised between
10-20 mph IAS faster than the B-17, but then it had to to be comfortable. The
crews hated having to fly in company with B-17s.

It's also easier to make lower aspect ratio wings of the same area stronger for the
same weight, because the stresses can be spread over a longer (and thicker) root,
which is one reason why a/c like the Stirling and B-17 have reputations for being
able to take lots of wing damage and survive, and why a/c like the B-24 had
opposite reps. However, the lower aspect ratio wing requires more area to get the
same lift at the same AoA, increasing drag.

A good job, Guy. If you don't mind, I'll dig a little deeper. into
some details.

The selection of Aspect Ratio and Wing Area are one of those tradeoff
deals. A high Aspect Ratio means that the Induced Drag (Drag due to
lift) is lower, for a given Lift Coefficient, and a low wing loading
means that the Coefficient of Lift can be lower. This is really
important at relatively low Equivalant Air Speeds, where the wing is
working hard to keep the airplane flying. As the speed goes up, the
Lift Coefficient decreases with the square of the speed, and the
Induced Drag coefficient drops with square of the lift coefficient, so
it decreases quite rapidly. Depending on what fraction of the total
drag is Induced Drag, Aspect Ratio might not be all that important.

I'll add the Stirling to the list, BTW. It should make an interesting
contrast to the Lancaster in terms of how the tradeoffs fall.

"Quest for Performance", L.K. Loftin, NASA History Office, 1985,
available online, has a quite good explanation and analysis of the
directions that designing high performance airplanes took through the
first 80 or so years. The data tables list the following values for
the various airplanes.

Airplane: Aspect Ratio Wing Loading Cruise Speed L/Dmax
B-17G 7.58 38.7 182 12.7
B-24J 11.55 53.4 215 12.9
B-29 11.50 69.1 253 16.8

Altitudes in cases would be 25,000', (Critical Altitude for the
turbosupercharged engines, in each case) and all speeds are True
Airspeed.

Note that the B-24 and B-29 have almost identical Aspect Ratios, but
the B-29 has a significantly higher wing loading. In general, this
means that the B-29 will have more induced drag than the B-24. But it
also cruises much faster. This is due to the lower total drag of the
airplane due to the much more streamlined shape.


--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster

In article ,
"Gord Beaman" ) writes:
Mike Marron wrote:


In other words, in your scenario above when the pilot increases
the wing angle of incidence (7-deg's), he simultaneously adjusts
his pitch and throttle settings as needed so as to remain stabilized
on the glideslope. He just doesn't gaily "pop the AoI switch" and
then react to what the airplane does...he thinks ahead and anticipates
what the airplane will do and plans accordingly (e.g: "fly the
plane" and pitch for airspeed power for altitude" etc.).


Of course Mike, I understand that but I just broke it down so
that it's easier for me to describe.

I still don't see what this AoI control will do _other_ than
give the pilot better downward visibility for landing and less
drag for high speed operation. Is there some other aspect that
I'm not seeing?...or is that it in a nutshell?...

No, that's pretty much it, really. The wing, for purposes of lift,
doesn't care particularly much what the attitude of teh fuselage is.
The variable incidence wing on the F-8 allowed better visibility, and,
as Guy said, better deck clearance, but it also allowed a shorter and
stronger main landing gear. This was pretty important in the
Crusader, as the loads on the gear as it trapped on the carriers of
the day were pretty much pushing the limit of what would work.

--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster

"Gord Beaman" wrote in message
...
Mike Marron wrote:


In other words, in your scenario above when the pilot increases
the wing angle of incidence (7-deg's), he simultaneously adjusts
his pitch and throttle settings as needed so as to remain stabilized
on the glideslope. He just doesn't gaily "pop the AoI switch" and
then react to what the airplane does...he thinks ahead and anticipates
what the airplane will do and plans accordingly (e.g: "fly the
plane" and pitch for airspeed power for altitude" etc.).


Of course Mike, I understand that but I just broke it down so
that it's easier for me to describe.

I still don't see what this AoI control will do _other_ than
give the pilot better downward visibility for landing and less
drag for high speed operation. Is there some other aspect that
I'm not seeing?...or is that it in a nutshell?...

a) Improved visibility over the nose, that's good.
b) Greater clearance for the tail, that's good.
c) Thrust line stays closer to horizontal. Good? Not sure...
Any thing else?

A & b would seem significant when making carrier landings.

In article , Guy Alcala
writes
Dave Eadsforth wrote:

snip

To enlarge on my 'thick wing section' description, and working from
memory of a book read long ago (which can be fatal), I recall that Davis
conceived of a wing section that was based on a mathematically deformed
circle, which he believed would give a more laminar flow. The thicker,
'teardrop-shaped' aerofoil section that resulted was also very useful
structurally, given that he wanted to combine it with a high aspect
ratio wing.

Of course, any wing section inboard of the engines was going to have its
airflow messed up considerably by a few minor essentials; like engine
nacelles and de-icing boots etc etc, but the wing outboard of the
engines may have performed as Davis believed it should during cruise.

snip

He was quite irritated that Consolidated didn't provide full covers for the
main
gear wheel wells, as he felt that defeated much of the drag reduction.

Guy

Some penny-pinching accountant at work perhaps?

I was always mystified by the fact that the Spitfire didn't get full
wheel-well covers until late in the war - they went to all that trouble
gluing split peas all over the wing to optimise the placement of flush
and round headed rivets and missed out on some thing that seems even
more obvious (unless the drag from the wheel well really was
inconsequential up to speeds of 400 mph or so - but that seems a bit
counter instinctive).

Cheers,

Dave

--
Dave Eadsforth

In article , Dave Eadsforth
writes
Some penny-pinching accountant at work perhaps?

I was always mystified by the fact that the Spitfire didn't get full
wheel-well covers until late in the war - they went to all that trouble
gluing split peas all over the wing to optimise the placement of flush
and round headed rivets and missed out on some thing that seems even
more obvious (unless the drag from the wheel well really was
inconsequential up to speeds of 400 mph or so - but that seems a bit
counter instinctive).

I think originally it simplified the gear retraction 'hydraulics'. The
first Spits had a hand pump to retract the gear, which required IIRC 27
pumps to fully retract it. I guess the full wheel well covers probably
came along with the retractable tail wheel (possibly more important?) as
well?

--
John

Guy alcala wrote in message

Vader states that the Mk VIIIs had the 'C' wing, which implies that
the Mk. IXs should have been able to be given LE tanks with little
difficulty. I'm under the impression that the substantive changes to
the Mk. VII/VIII were in the fuselage, and except for the tanks the
wings were identical. Does anyone actually KNOW what the
structural/internal changes were from the Mk.V/IX etc. to the Mk.
VII/VIII? We all know about the tail wheel, but there had to be more
than that.


More information from Morgan and Shacklady,
Spitfire weights, tare / take off / maximum

VA 4,981 / 6,416 / 6,700
VB 5,065 / 6,622 / 6,700
VC (B wing) 5,081 / 6,785 / 7,300
VC (C Wing) 5,081 / 7,106.5 / 7,300

So if this is correct an extra 16 pounds was added, presumably
to the fuselage, between the B and C versions. The book is also
saying the VC version is not defined by the wings fitted, A or B
or C wings, there is something else. The VC was a definite
change, and able to carry 600 pounds more weight, presumably
mainly by strengthening the undercarriage.

The second production VC AA874 (Merlin 45) was weighed with
A, then B then C wings, weights in pounds, CoG in inches

wing / tare / tare CoG / all up weight / all up CoG
A / 5,048 / 2.31 / 6,499 / 10.9
B / 5,048 / 2.31 / 6,737 / 10.9
C / 5,048 / 2.31 / 6,969 / 7.65

The mark VI, the pressure cabin version of the V, weights,

tare 5,227 pounds, take off 6,797, maximum 6,850.

AB450 was the prototype mark VII. It was a standard mark V
with the following modifications, extended wing tips, 4 bladed
propeller, retractable tail wheel, tail parachute fin guard, Merlin
61 with twin underwing radiators.

The certificate of design general description was "This
aeroplane is the prototype of the F Mk VII and F Mk VIII
production Spitfires. Components of existing types with some
modifications as used as indicated. Fuselage Spitfire Mk VI
with the forward bay reinforced for Merlin 61 engine. Spitfire
F Mk 20 tail unit, Spitfire Mk V elevator and rudder. Mainplane
Spitfire F VC with spar flanges reinforced and lead ballast
added in outer portions of the wings. Main chassis Spitfire
F Mk VC leg and support structure. Spitfire F Mk VII production
wheel and tyre equipment. Tail chassis, Spitfire F Mk VII
production. Tare weight 5,201 pounds, maximum all up 8,000."

Production VII tare weight 5,947 pounds or 5,887 pounds,
depending on the hood used, take off 7,928 pounds, maximum
8,000 pounds. This indicates there probably was some fuselage
strengthening between the prototype and production.

Morgan and Shacklady state the mark VIII had the fuselage further
strengthened over the mark VII, with the VIII weights as Tare 5,806
pounds, take off 7,779 pounds maximum 8,000 pounds. This looks
like the VII without the extra wing tips and pressure cabin gear.

Mark VIII 2 cannon and 4 browning, weights in pounds and CG in
inches tare 5,861 and 0.2 landing 6,710 and 4.9, normal load
7,831 and 5.9, 30 gallon overload tank 8,131 and 6.4, 90
gallon overload tank 8,648 and 7.0. The figures are repeated
for a 4 cannon version, interestingly tare weight is the same
but all the other weights are around 200 pounds more, and the
CG figures 0.1 to 0.3 greater. CG measured aft of datum.
Since a pair of 20 mm cannons came in at around 200 pounds
and 4 brownings at around 100 pounds this would seem to
indicate tare weights are with the armament removed.

F Mark IX tare 5,816 pounds, take off 7,295.5 pounds, maximum
7,500 pounds. After notes about overload tanks and bombs comes
the entry "ballast 92.5".

F IXE tare 5,816, take off 7,181.5, max 7,500.

Perhaps a look at the PR IV which was the PR version of the V
and normally had the cameras located behind the cockpit, they
also carried radio, TR 1133 or 1143.

Tankage front fuselage 48 upper 37 lower, same as mark V,
2 x wing leading edge tanks 66.5 gallons each, total 218
gallons. Oil tank 18 gallons in port wing between ribs 9 and 12.

Tare weight 4,935 pounds, take off weight 7,148 pounds (W),
7,155 (X), 7,119.5 (Y). Max permissible 6,500 pounds (yes
six thousand five hundred, a typo I presume). Tail ballast 17.5
pounds.

W version 2 x F8 20 inch split vertical fanned between fuselage
frames 13 and 15 inclined 10 degrees to the vertical and 20
degrees to each other.

X version 2 F24 14 split vertical fanned and 1 F24 8 or 14 inch
oblique mounted as W version with oblique over front F24.
Inclined 8.5 degrees to the vertical and 17 degrees to each other.

Y version, F52 36 inch vertical used only for bomb damage
assessment, mounted between frames 13 and 14.

PR VII, same as IV except,

Tankage front fuselage 48 upper 37 lower, same as mark V,
rear fuselage 29, total 114. Oil 5.8 gallon, in tank under engine.
No radio. Weights tare 4,985 pounds, take off 6,584 pounds,
maximum 6,590. CoG moved forward as fuel was consumed.

Cameras, G installation, F24 5 or 8 inch vertical (front) and F24
8 or 14 inch vertical (rear) between frames 13 and 14 and 1 F24
8 or 14 inch oblique mounted above front camera.

Some PR VIII had A wing armament.

From Spitfire by Peter Moss, the initial hand converted PR
versions from Spitfire I had a 29 gallon fuel tank under the
pilot's seat and a 64 pound camera installation behind
the cockpit, no radio though. It all worked because there
was 32 pounds of removable ballast in the tail to compensate
for the mark I moving to a heavier 3 bladed propeller.

If the ballast figures are correct there is obviously some room
for extra fuselage tanks, the maximum take off weight comes
into play though. It appears 315 British gallons of 100 octane
fuel comes to 2,240 pounds, for 80 Octane fuel 300 gallons
weigh 2,240 pounds.

Geoffrey Sinclair
Remove the nb for email.

Geoffrey Sinclair wrote in message ...

The Stirling
wingspan was 99 feet 1 inch versus the B-17 103 feet 9 inches, it was
also the thickest wing, able to carry bombs in cells within the inner wing.
three cells on each side capable of carrying 500 pound bombs at least.


I should add the Halifax also had 3 cells in each wing for 500
pound bombs, from Halifax : an illustrated history of a classic
World War 2 bomber by Kenneth A. Merrick.

Geoffrey Sinclair
Remove the nb for email.

(Peter Stickney) wrote:

[B-24 vs. B-29 wing specs snipped for brevity]

But it also cruises much faster. This is due to the lower total drag
of the airplane due to the much more streamlined shape.

Not to mention the Superfort's extra *4,000* total horsepower and four
humongous four-blade 17-ft. diameter props!

-Mike Marron

"John Keeney" wrote:
"Gord Beaman" wrote:
Mike Marron wrote:

In other words, in your scenario above when the pilot increases
the wing angle of incidence (7-deg's), he simultaneously adjusts
his pitch and throttle settings as needed so as to remain stabilized
on the glideslope. He just doesn't gaily "pop the AoI switch" and
then react to what the airplane does...he thinks ahead and anticipates
what the airplane will do and plans accordingly (e.g: "fly the
plane" and pitch for airspeed power for altitude" etc.).

Of course Mike, I understand that but I just broke it down so
that it's easier for me to describe.

I still don't see what this AoI control will do _other_ than
give the pilot better downward visibility for landing and less
drag for high speed operation. Is there some other aspect that
I'm not seeing?...or is that it in a nutshell?...

As I mentioned in my response to you (the important part that you
snipped), besides just increasing the visibility, the variable
incidence wing also enabled the sleek and very fast fighter to
maintain the slower speeds required for carrier ops.

In other words Gord, the variable incidence wasn't designed to give
the F-8 "less drag for high speed operation," it was designed to give
the F-8 MORE drag (as the result of more LIFT) for SLOW speed
operation in order to land aboard carriers.

Also, if you peddle back to that website that you posted depicting
a close-up of the Crusader's wing in the raised position, you will
clearly see how the raised portion of the wing assembly directly
above the fuselage is flat as a sheet of plywood and protrudes
right into the relative wind -- effectively functioning as a speed
brake.

a) Improved visibility over the nose, that's good.
b) Greater clearance for the tail, that's good.
c) Thrust line stays closer to horizontal. Good? Not sure...
Any thing else?

I could be wrong, but I don't see any reason why the thrust line
staying closer to horizontal would be a "bad" thing. In the event
of a waveoff the pilot simply has to light the burner and go around
w/o making any drastic adjustments in angle of attack because
the raised wing is already configured for takeoff.

A & b would seem significant when making carrier landings.

Agreed. Although the 20-30 kt. wind over the deck is laminar
and smooth, the part curling down over the fantail is not which
can cause a sudden increase in rate of sink at precisely the
most inopportune time (e.g: ramp strike!)

-Mike Marron

In article , Mike Marron
writes
Not to mention the Superfort's extra *4,000* total horsepower and four
humongous four-blade 17-ft. diameter props!

That brings a comparison between the B-29 and Shackleton wings/engines
into the equation I guess.

--
John