Aircraft Roll Rate
Michael Turton
What is the "roll rate" of an aircraft and why is it
important in the kind of air-to-air combat seen in WWII?
Mike Turton
Steve
On 23 Oct 1997 00:10:25 GMT, this appeared in the neighbourhood of
mtu...@ms1.showtower.com.tw (Michael Turton)'s address:
> What is the "roll rate" of an aircraft and why is it
>important in the kind of air-to-air combat seen in WWII?
The 'roll rate' of an aircraft is the rate at which it can change its
angle of bank, measured in degrees per second. This is as distinct
from 'turn rate', which measures the change in the aircraft's heading
in degrees/sec.
Roll rate is very important in close air combat, possibly equally
important as the more commonly referred to turn rate, due to the
constant twisting and changes of direction of the aircraft. An
aircraft with a very high roll rate is able to alter its direction of
turn and to manoeuver more rapidly than an aircraft which may turn
fast, but is unable to roll as quickly.
-------------------------------------------------------
Steve Long
to reply please remove the NOSPAM from my email address
Donald Phillipson
Michael Turton (mtu...@ms1.showtower.com.tw) writes:
> What is the "roll rate" of an aircraft and why is it
> important in the kind of air-to-air combat seen in WWII?
The roll rate of an aircraft also indicates how fast it can
turn, because WW2 aircraft turned more on their ailerons
than their rudders (which produce a skidding turn if used
alone.) I.e. roll rate is a rule of thumb for manoeuvrability.
This is important in dog-fighting. Aviators discovered in WW1 the best
fighter aircraft for dog-fighting is relatively unstable, i.e. may
turn quickly at any moment. Some hot WW1 fighters e.g. Sopwith
Camel were notorious for killing inexperienced or inattentive
pilots, but were preferred by experienced pilots because of
their responsiveness in a dog-fight.
But this feature may impede other sorts of attack, e.g.
the single fast pass when attackers dive on a formation and
dive away to regroup elsewhere, rather than staying around to dog-fight.
Thus, as usual, aircraft design is a trade-off between various
qualities, here stability and responsiveness to the controls.
--
| Donald Phillipson, 4180 Boundary Road, Carlsbad Springs, |
| Ontario, Canada, K0A 1K0, tel. 613 822 0734 |
Endymion
Roll rate is the quickness with which an aircraft rotates about its
longitudinal axis, i.e., raises one wing and lowers the other. Since turns
are banked, roll rate determines how quickly an aircraft can begin turning.
Thus a Spitfire, with a good sustained turn but poor roll rate, could,
given time, turn inside an FW190, with a mediocre turn but high roll rate,
while the FW could make a quicker snap turn.
I have also read that FW190 pilots (and presumably pilots of other planes
with similar performance, like the F4U) took advantage of this in evading a
following plane by rolling a bit one way, thus faking the slower rolling
plane into banking the same way, then quickly rolling and turning the
opposite way. The following Spit would be unable to reverse its bank
quickly enough to keep up.
--
Endymion
utu...@michie.com
"Let us drink - who would not? - Since, through life's varied round,
In the goblet alone no deception is found."
David William Glasser
On 23 Oct 1997 00:10:25 GMT, mtu...@ms1.showtower.com.tw (Michael
Turton) wrote:
> What is the "roll rate" of an aircraft and why is it
>important in the kind of air-to-air combat seen in WWII?
>
>
An aircraft 'rolls' along its long axis as a flight maneuver, the
wingtips describing a partial helix around the flight path. Turning
and banking quickly in a dogfight requires some degree of roll to
perform. The faster the roll rate of an aircraft, the more quickly it
can perform a number of important maneuvers. For example, fighters
without fuel injection engines had to roll onto their backs to perform
a power dive. Engine torque on some fighters, particularly those with
single, rotary engines, could allow for quicker rolls clockwise rolls.
The most effective dogfighting aircraft were known to be very
responsive to slight movements of the stick -- a useful characteristic
to seasoned pilots but dangerous to rookies, especially while taking
off and landing. A wingtip could catch on the ground and result in a
cartwheeling crash.
David William Glasser
Fencing Master; BFC/SKS Bergen 1976 BLZ/LLZ Bonn 1977
University of Wisconsin -- Madison Dept. of Kinesiology
gla...@facstaff.wisc.edu
Charles K. Scott
In article <62m4lh$10ra$1...@nntp6.u.washington.edu>
mtu...@ms1.showtower.com.tw (Michael Turton) writes:
> What is the "roll rate" of an aircraft and why is it
> important in the kind of air-to-air combat seen in WWII?
>
> Mike Turton
A good question Mike and one that usually leads to long debates on "my
fighter rolls faster than your fighter" in this group.
Roll rate refers to how fast an airplane can bank it's wings. It's
often given as a number of degrees per second. Being able to snap from
horizontal completely around to inverted and back to horizontal again
(always rotating in the same direction) in one second is considered
blindingly fast. There are practical limits for humans as to how fast
the airplane can roll. Roll too fast and the brain can become
disoriented.
In WWII, most aircraft rolled at very different rates depending on how
fast they were going. At middle speeds, like around 250 mph, most
aircraft realised their optimal roll speed. At higher speeds the
ailerons became increasingly hard to operate and roll rate became a
matter of how strong the pilot was. In the Spitfire, it was often the
case that high speed maneuvering required two hands to force the stick
over.
The P-38 had such heavy aileron forces that it used a wheel rather than
a stick to increase the force of the pilots input.
At higher speeds, combat maneuvering could ressemble a slow motion
ballet, one author wrote that to go from one 45¡ bank to the other at
350 mph in the Spitfire required FOUR SECONDS. (Fighter, by Len
Deighton).
Later in the war it was discovered that the fabric covered ailerons
were deforming at speed causing some of the heavy forces. One of the
"fixes" that occured to the Mark V Spitfire was the switch to metal
ailerons which reduced stick forces and increased the rate of roll at
high speed.
However, the majority of fighter to fighter combats were extremely
fleeting, not permitting the sort "dogfighting" so often discussed. To
spend a lot of time maneuvering for a shot was to become a target
yourself so it wasn't done often, although combat maneuvering did
occur.
Fighters were a compromise blend of flight characteristics. As has
been mentioned, they were designed to be deliberately unstable so as to
facilitate instantaneous change of direction. However, this mitigated
against it's role as a long range escort; it was extremely tiring to
fly for long distances if you constantly had to correct flight
direction. The Mustang, starting with the B model, was far more stable
than the Me 109 or the Spitfire. Different roles, different flight
characteristics.
Corky Scott
Michael Turton
In article <62qicv$cc2$1...@nntp6.u.washington.edu>,
Charles...@Dartmouth.EDU (Charles K. Scott) wrote:
>In article <62m4lh$10ra$1...@nntp6.u.washington.edu>
>mtu...@ms1.showtower.com.tw (Michael Turton) writes:
>
>> What is the "roll rate" of an aircraft and why is it
>> important in the kind of air-to-air combat seen in WWII?
>>
>> Mike Turton
>
>A good question Mike and one that usually leads to long debates on "my
>fighter rolls faster than your fighter" in this group.
>
Thanks to everyone who took the time to explain this to me. I was looking
through E. Gustin's glorious site on aircraft, which is just wonderful, and
realized I didn't know what the term meant.
Someone, I think Dan Ford, posted earlier that the US Army Air Force
conducted postwar flyoffs of the various Axis fighters. Is that report on
the Web somewhere? I can't find it.
Mike Turton
C.C. Jordan
On 24 Oct 1997 16:29:19 GMT, Charles...@Dartmouth.EDU (Charles K. Scott)
wrote:
[snip]
>At higher speeds, combat maneuvering could ressemble a slow motion
>ballet, one author wrote that to go from one 45¡ bank to the other at
>350 mph in the Spitfire required FOUR SECONDS. (Fighter, by Len
>Deighton).
American fighter ace Robert Johnson describes how he was able to
out maneuver the Spitfire by using the Thunderbolt's much higher
rate of roll. He states in his book "Thunderbolt", that the P-47D
had a roll rate better than twice that of a Spitfire. In friendly mock
dogfights over Britain, he would find a Spitfire, using it's better rate
of turn, sliding into postion behind him. At this point, he would execute
a series of snap rolls to one side. Each roll provided him with additional
lateral displacement ( moving away to the side). If the Spit did not follow,
Johnson would half roll into a split S and disengage. The Spit not having
a prayer of keeping up. If the Spitfire tried to follow, it would scrub off
speed rapidly as the T-Bolt pulled away. Johnson would wait until the
Spit began another roll, then he would slap the stick in the opposite direction,
rolling once, then pushing the nose down. As the T-bolt accelerated away,
Johnson would pull up into a zoom climb, through a loop and dive in
on the now slow moving Spitfire from the 12 o'clock high position. The
Brit in the Spitfire was always astounded to see the big P-47 rushing in
through the top of his canopy. Johnson had several opportunities to
fly various marks of the Spitfire. He commented that they were wonderfull
to fly, easily out turning the T-Bolt. But they could not dive or roll very
well. He was especially shocked when he rolled a Mk V inverted and had
the engine konk out. He later was told that the carburetor was not designed for
prolonged inverted flight. He thought that a bad idea in a fighter plane.
[snip]
>
>Fighters were a compromise blend of flight characteristics. As has
>been mentioned, they were designed to be deliberately unstable so as to
>facilitate instantaneous change of direction. However, this mitigated
>against it's role as a long range escort; it was extremely tiring to
>fly for long distances if you constantly had to correct flight
>direction. The Mustang, starting with the B model, was far more stable
>than the Me 109 or the Spitfire. Different roles, different flight
>characteristics.
>
>Corky Scott
You may find it of interest that American pilots, transitioning from
P-38's and P-47's to the Mustang, thought the Mustang required
constant attention at the controls. This was the result of coming
from very large and stable fighters to the much smaller and more
"nervous" P-51. It's all a question of perspective.
Best regards,
C.C. Jordan
"Passion and prejudice govern the world; only
under the name of reason".
John Wesley
http://www.Aerodyne-controls.com
Rob Davis
Remove MAPSON if replying by email
> In WWII, most aircraft rolled at very different rates depending on how
> fast they were going. At middle speeds, like around 250 mph, most
Jonathan Falconer's STIRLING AT WAR claims that the Stirling
would out-turn a Hurricane. I can't think that this could
possibly be true, bearing in mind the comparative sizes.
Anyone else care to input on this?
> Later in the war it was discovered that the fabric covered ailerons
> were deforming at speed causing some of the heavy forces. One of the
Yes, the same problem occurred on Lancasters. At the flight
testing stage, some aircraft were repeatedly dived to the maximum
diving speed (375 mph) and the airframe checked afterwards.
After one fatal crash, it transpired that ballooning of the
facbric-covered elevators severely reduced their effectiveness,
although the aircraft could be pulled out by using the elevator
trim tabs, which is no way to treat an aeroplane except in an
emergency.
After metal skinned elevators were fitted, the problem went away.
source LANCASTER AT WAR II (article by Sandy Jack, Avro's staff)
Rob Davis MSc MIAP
Anstey, Leicester UK. 0976 379489
Alphons Hilgers
Can anyone give hard factual data about SS Frontarbeiter and the units they
were added to?
Charles K. Scott
In article <637oo3$ocu$1...@nntp6.u.washington.edu>
Bill MacArthur <bil...@uwindsor.ca> writes:
> Later versions of the Spitfire had the eliptical ends of the wings
> squared off to increase the roll rate which was performance problem in
> the earlier Spits. Judging from the performance of the Spit XIV it was a
> great success. IIRC that was one performance advantage that the P-47 had
> over its opponents was its high roll rate.
There was at least one model of Spitfire that had it's wings clipped to
increase it's low altitude performance so as to improve it's chances
against the low altitude attacks on Britain by Focke Wulf 190
fighter/bombers. These were hard to stop because they came in on the
deck at high speed, dropped their bomb and headed straight back. The
clipped wings were less to increase the roll rate than to decrease drag
for a higher low altitude speed.
There were actually several advantages the P-47 had over it's
adversaries. An incredible dive speed that no prop engined German
fighter could better. It's roll rate which seemed at least as good as
that of the Focke Wulf. 8 .50 caliber machine guns which made even a
short burst lethal. And possibly the most robust construction of any
fighter in WWII.
In one anecdote, a German fighter pilot related how he and his buddies
trapped a P-47 down low and had it boxed in so that it could not
escape. It tried to flee rolling right and left everytime the pursuing
fighters shot at it. It was hit repeatedly, time and time again but
would not go down. The Thunderbolt pilot's skill greatly impressed the
squadron leader as it wracked away from their guns time after time.
Finally the american took a fatal hit and lost speed and bellied in.
The German pilots all pulled up, circled the wreck and observed the
pilot climb out. They landed at a nearby airfield and rushed over to
meet the pilot.
The guy wrote that he was disappointed. The pilot was a freckle faced
youngster who was popping bubble gum while the German tried to talk
with him and appeared uninterested in conversation.
What impressed the flight leader was to see someone so young so
skillful at the controls, but also how much trouble and gunfire it took
to down that Thunderbolt.
Corky Scott