Bearcat roll rate

[spicmart]

ChatGPT says the Bearcat was the fastest rolling piston-engined fighter bar none. True?

 

[ThomasP]

No.

 

[SaparotRob]

No.

That's an answer I can understand.

 

[GregP]

I have never seen a rool rate comparison chart that included the Bearcat. I have never seen a pb/2V value for the Bearcat, either.

But, it's something to go look into ...

I DO know people who have flown many different piston fighters, including foreign ones. The main question is whether or not they have ever thought to notice higher roll rates in many of them, ecpecially comparitively. Personally, I have flown Cessnas, Pipers, and a Stearman or two, and I never thought to notice which one rolls best out of the population.

 

[Shortround6]

Not too many pilots try for max rate of roll except in combat or in aerobatic competitions.
Or trying to measure rate of accelerating to max roll rate.

I have no idea if modern warbirds are flown with ballast representing guns/ammo or have dummy guns fitted for show (or just barrels?) but taking around 300lbs out of the mid point of each wing is going to change things. Of course taking roughly the same amount of weight out the wings of several different warbirds is going to equalize things somewhat.
Add roll rates (or acceleration) changes with speed, often severely.

 

[NTGray]

When thinking about maneuverability, it always seemed to me (a non-pilot) that there were really just two factors involved. First, how quickly can the plane roll (how much time does it take to get sideways), and, second, how many Gs can it pull once it has rolled 90° and starts to turn? This then translates to how much time it takes to complete a 90° (or 180°) turn. The Zero was supposed to be pretty good at that particular trick; could a Bearcat beat it? Which plane or planes could do it the quickest?

 

[smutny]

A few years ago there was a very lively discussion in the aerobatic chat channels about roll rates. One intrepid individual, Spencer Suderman, spent a lot of time analyzing video footage, frame by frame, to determine roll rates on a wide variety of aerobatic airplanes. Unfortunately, no Bearcat pilots sent in any video, but here are a couple of the warbird numbers:

	Video FPS	Roll 1 Frames	Roll Rate degrees/second		Roll 2 Frames	Roll Rate degrees/second		Notes
War Birds
AT-6D	60	190	57		193	56		150 mph reported by pilot
Harvard Mark IV	24	65	66					160 Kts reported by pillot
T-6G	30	74	73					Metal Ailerons
P-51 Mustang	30	58	93					Pilot reported 200 kts
F4U Corsair	30	67	81					Pilot reported 160 kts
T-33	30	74	73

A couple of the general consensus outcomes were that pilots often over-estimated aircraft performance, and modern digital cameras with high frame rates are far better suited for this analysis than older film based cameras. The data isn't scientific accurate, a lot of variables, but makes for some good hangar flying.

 

[GregP]

When thinking about maneuverability, it always seemed to me (a non-pilot) that there were really just two factors involved. First, how quickly can the plane roll (how much time does it take to get sideways), and, second, how many Gs can it pull once it has rolled 90° and starts to turn? This then translates to how much time it takes to complete a 90° (or 180°) turn. The Zero was supposed to be pretty good at that particular trick; could a Bearcat beat it? Which plane or planes could do it the quickest?

The available g-force changes with airspeed, weight, and altitude. Here is an aircraft VG diagram, valid for a particular weight and altuitude.

If you are in air, then the part of the cruve below 1 g can be experienced. If you are sitting still on the ground, you are below Vs (stall speed) and cannot experience less than 1 g since you can't get away from gravity. If you are airborne (above Vs) and below point A, then your g-available is less than or equal to the red line value. In the diagram above, if you go vertically upward from 80 knots, you intersect the red line on the positive side at about +2.3 g and the negative side intersects at about -1.2 g. So, you have anywhere from -1.2 g to about +2.3 g available. If you try to pull more positive g, you stall. If you try to push more negative g, you stall.

It continues that way up to point A, called Corner velocity. At point A, the g-available on the positive side just equals the structural strength. If you pull more g than that, you can and likely will damage the airplane. If you pull to many g's above that point, you will cause structural failure.

Point D, or Vd, is the demonstrated maximum dive velocity. If you exceed that speed by much, the dynamic pressure will cause structural failure and the airplane will come apart.

So, basically, inside the red line envelope is available to you while flying. Outside the red line envelope is "iffy" and potentially fatal. The phrase "pushing the envelope" comes from this diagram and means you are at or outside the diagram's red line envelope.

This envelope is valid for a particular weight and altitude combination and changes if you change either weight or altitude.

This is not telling most people in here anything they don't already know but, sometimes visiting the basics can be fun.

Edit: The diagram above shows up in edit mode and goes away when I hit save. Sorry about that. Re-posted in bitmap.

 

[NTGray]

Once again I find myself getting educated by this forum.

When picturing in my mind a warbird rolling in combat, I see the best ones doing a 360 roll in just about 1½ seconds. But now I'm reading this thread and also doing some looking up on my own, and I'm reading that even the Zero had a maximum roll rate of about 100° per second, meaning it would take about 3½ seconds for a Zero to do a 360. That seems painfully slow to me.

But I did find that one model of the Pitts Special can do a full roll in a little over one second, which is about what I used to think was normal for good fighters. Silly me. Now I know better.

 

[smutny]

... I'm reading that even the Zero had a maximum roll rate of about 100° per second, meaning it would take about 3½ seconds for a Zero to do a 360. That seems painfully slow to me.

But I did find that one model of the Pitts Special can do a full roll in a little over one second, which is about what I used to think was normal for good fighters. Silly me. Now I know better.

I'd surmise that the 100 degrees/second number for the Zero is high. Again, the analysis done was a great learning session on roll guestimates. It all started with the legend of the T-38 doing 720 degrees per second. Alas, no T-38 full deflection video was ever submitted.

When I first flew the WolfPitts, I smacked my head on the canopy when I did my first full deflection roll. Started wearing a helmet again after that....

Here's a chart plotting all the roll rates of submitted videos.

 

[eagledad]

Gentlemen,

F8F-1 roll rate found near the end of this document.

FYI

Eagledad

 

[ThomasP]

So a max roll rate of ~116°/sec to the left, and ~110°/sec to the right - both directions with full stick deflection (ie greater than 30 lbf side stick force - probably about 45 lbf?).

 

[spicmart]

When thinking about maneuverability, it always seemed to me (a non-pilot) that there were really just two factors involved. First, how quickly can the plane roll (how much time does it take to get sideways), and, second, how many Gs can it pull once it has rolled 90° and starts to turn? This then translates to how much time it takes to complete a 90° (or 180°) turn. The Zero was supposed to be pretty good at that particular trick; could a Bearcat beat it? Which plane or planes could do it the quickest?

The Russians conducted specific turn tests at 1000 m of altitude as their fighter doctrine emphasized good turn performance (just like the Japanese) in contrast to German doctrine which never seemed to care too much about this parameter. Instead they opted for high wing loading to give their fighters a plus in speed but which degraded turn rate.
Both Russian top tier fighters La-7 and Yak-3 rolled arguably faster than the Bearcat and any Japanese fighter because of their much smaller dimensions. The Yak-3 was considered to be able to turn the tightest (17 seconds for a 360° turn iirc) and being the most nimble WW2 fighter as well.
Not sure how worse or better the Japanese fighters were with them in general having the lowest wing load.
Their roll rate deteriorates fastest at speed.

 

[Holtzauge]

An interesting thing to note with roll rates is that it's not enough just to have an IAS speed since the roll rate for an aircraft will increase with altitude for any specified IAS. This is why for example NACA reports usually also mention an altitude in conjunction with a roll rate number, e.g. in NACA report 868 which has a comparison chart for the roll rates for a number of different aircraft comparing them at 10,000 ft.

 

[Holtzauge]

But 110-116 deg/s roll rate at 30 lb stick force for the F8F is good: Of all WW2 fighters the Fw-190 seems to reign supreme with over 160 deg/s, but that is at a 50 lb stick force.

I always wondered who did these tests: Who on earth manages to shove the stick sideways (in a WW2 fighter your arm will be quite forward when you are neutral in pitch) with a 50 lb force long enough to do a complete roll, say 4 s with 90 deg/s?

From NACA report 868:

 

[special ed]

Could fear and panic increase stick force?

 

[Holtzauge]

Could fear and panic increase stick force?

Absolutely. As a test engineer it's always a good idea to have something on your test pilots for motivation: Like juicy pictures from their last overseas deployment.

 

[Clayton Magnet]

Stick force values seem like a red herring to me in these tests. If the ailerons are at maximum deflection, then the control column will be on the physical stops. Doesn't matter if the pilot is holding it on the stops at 30 pounds, or 50 pounds.
Perhaps with the increase of airspeed, some of the aircraft simply didn't reach maximum deflection at or before 50 lbs of stick force

 

[Holtzauge]

Stick force values seem like a red herring to me in these tests. If the ailerons are at maximum deflection, then the control column will be on the physical stops. Doesn't matter if the pilot is holding it on the stops at 30 pounds, or 50 pounds.
Perhaps with the increase of airspeed, some of the aircraft simply didn't reach maximum deflection at or before 50 lbs of stick force

Sure, the stick force is not the limiting factor a lower speeds but it does become a factor above a certain speed. If you look at the figure above from the NACA 868 report, some curves have a marked "roof" point.

This is the point at which the pilot exerting a 50 lb force on the stick is just strong enough to overcome the aileron force and apply full aileron deflection. But above this speed he cannot , and the 50 lb is only good for a gradually decreasing aileron deflection. So below this speed he is not force limited, and he can get the full aileron deflection with less force.

Taking the Fw-190 as an example, below 255 mph the pilot can deflect the ailerons fully with less than 50 lb force but above 255 mph he is force limited and the 50 lb is not enough to deflect even the Fw-190's well balanced ailerons fully, and hence the lower and lower roll rate as speed goes up.

 

[smutny]

The truth of the matter is that we're trying to get down in the weeds on a subject that we only have a 20,000 foot, incomplete, view of. There are too many variables to make a firm comparison.

• Type of roll (slow or aileron)? If aileron, were all pitch-ups the same?
• Which roll was used for data? First roll is always slowest on account of stick movement.
• How was breakout force measured, calculated or by mechanical instrument?
• How were the rolls timed? By pilot, by observer, by film? All have a lot of room for error. Or were they all just calculated?
• etc... etc... etc...

So if you're looking for a solid, definitive answer, you're not going to find it in the data we have at our disposal.