Relative Rolling Characteristics of WWII Fighters

[GregP]

Saw a post (forget the exact one ... was something like "Fw 190: The Roots of the Great Roll Rate" or something to that effect) and it had a chart of the rolling performance of various WWII fighters, mostly ETO with the Japanese Zero included. The speed went from 160 mph to 390mph and there were chart lines showing the rolling performance.

The thread pretty much ended with that chart.

The chart was Table 47 from NACA Report No. 868 and I dutifully put it into Excel to start a rolling model and then decided to get the whole report to see which model Fw 190 and Zero were used for the tests.

Turns out the entire chart was done in an NACA wind tunnel using pb/2V values obtainable at 10,000 feet with a 50-pound stick side force. No real aircraft were used in generating the chart, just wind tunnel models ... so I doubt seriously the chart is correct for real-life aircraft since I, myself, can put more than a 50-pound side force on a P-51 stick (using both hands), and most combats in the ETO were not at 10,000 feet or the P-39 and P-40 would have been right there as great fighters even without the turbos. The P-51 also has three possible deflections for the ailerons, settable by the crew chief, as has been pointed out in the past in here.

Moral of the story is if you take a chart out of context, you don't really know what you are seeing! Caveat Emptor ... or something like that. If you google NACA Report No. 868, you can download your own copy and check it out.

I'd still like to see comparative roll charts of real planes measured in actual flight with real pilots flying them! Oh yeah ... throw in a Bf 109 for completeness since it is conspicuous by its absence in an otherwise mostly ETO aircraft grouping, except for the "Zero".

I believe the report was dated 1947, but the snippet I can get as a pdf was undated and started on page 125 or so.

Cheers.

 

[GregP]

Reminds me of the old Sears Diehard commercial on US television years ago. They drove a Chevrolet Impala out onto a frozen lake and the announcers said, "International Falls Minnesota, a car sits on a frozen lake for three months and then we start it with a Diehard!" The car started, of course.

I was curious and sent off for the test documentaion since I had never HEARD of a battery that could do what I was seeing.

Got the docs. They had tuned up the Chevy, driven it out onto the frozen lake, drained the oil and removed the battery. Three months later they went out, poured in new, room-temperature oil, installed a new, room-temperature Diehard battery, and the car started.

Now THAT I could believe!

 

[Aozora]

The report can be found here: http://naca.central.cranfield.ac.uk/reports/1947/naca-report-868.pdf

 

[GregP]

Thanks Aozora, I now have a complete download insead of a snippet on roll rates. Appreciate it.

 

[VBF-13]

I remember that Sears Diehard commercial. Greg, do you remember the movie, "The Flight of the Phoenix," with Jimmy Stewart? Do you remember the engineer, he built model airplanes?

It worked, though. In the movie.

 

[GregP]

Yah. Great movie and still is. Our museum supplied the O-47 to finish the flim when Paul Matz crashed the dedicated plane in an uneeded take. Paul died needlessly ... really an unforgivable thing. The director should be whipped but he is dead. OK.

The thing is, in the chart, they didn't model the rolling at a realistic altitude for combat in Europe, relied on pb/2V at 10,000 feet, and 50 pounds of stick force. I have no idea if the models, ailerons, gap seals, hinge lines, aileron cross section, etc. were correct and were analyzed correctly ... and neither does anyone else except the guys who did the test.

As a result, I have my doubts though, if the models were good, the relative position of the planes would be about the same even if the roll rates differ.

I assume they at LEAST got the aileron deflections correct ... but have no knowledge of that.

 

[Hop]

Turns out the entire chart was done in an NACA wind tunnel using pb/2V values obtainable at 10,000 feet with a 50-pound stick side force. No real aircraft were used in generating the chart, just wind tunnel models ... so I doubt seriously the chart is correct for real-life aircraft

The Spitfire and FW 190 figures come from RAE tests of actual aircraft. I can't say about the rest of the aircraft, but I think they come from a variety of real world tests.

I, myself, can put more than a 50-pound side force on a P-51 stick (using both hands), and most combats in the ETO were not at 10,000 feet

You have to standardise figures or you won't have a basis for comparison. Whilst it should be possible to put more than 50 lbs force in some aircraft, how long can a pilot continue to put that much effort in? Altitude shouldn't make much difference to the results as they are given for IAS anyway. The relative performance of the aircraft shouldn't change at all with altitude.

 

[Tante Ju]

Altitude shouldn't make much difference to the results as they are given for IAS anyway. The relative performance of the aircraft shouldn't change at all with altitude.

Actually roll increases with altitude considerably at the same IAS.

 

[tyrodtom]

If you can apply 50 lbs or more of force against a stick under normal conditions, how much could you apply under combat conditions?
With adrenaline in your bloodstream you're going to be a lot stronger than normal.

A good example of that, the Zero, poor roller at higher airspeeds, but Saburo Sakai managed to avoid a horde of Hellcats for several minutes, mostly by rolling out of their line of fire, and i'm betting he wasn't at a low airspeed. So a noted slow rolling aircraft manages to survive, with the aid of a excellant pilot, and adrenaline.

 

[razor1uk]

Indeed so , never underestimate a human when he/her/they are pecieving things as life-threatening; complacentcy always favours the underdog in a situation so long as they know they're the underdog, although not what they do different because they know this...

 

[GregP]

Relative performance does change with altitude. At high altitudes, span loading and aspect ratio come into play for maneuverability. Long wingspan planes come into their own at very high altitude where they are relative slugs at low altitude, at least roll-wise. Of course, the "come into their own" part is only relative to shorter-span aircaft that degrade seriously as they get to their ceiling.

I've never heard anyone say that rolling performance increases with altitude before at the same IAS and never investigated it. Only for one design at a time; never a comparative look between competing designs or among several. However, it seems worthy of a look see when I get around to it.

Regarding Saburo Sakai, I met him once at the old Doug Champlin Fighter Museum in Mesa, Arizona, and he told that story that night. He was convinced that fighter pilots perform as they train, and nobody trained them to deal with a fighter rolling away from them but not really PULLING away. They all expected him to roll a bit say, 45 - 60°, and then pull hard ... and he didn't do that. Instead he rolled all the way around and didn't pull away. Was a very nice and gracious man to speak with and was well liked by all there, even former WWII GI's.

He went for a ride in Bill Hane's P-51D "Ho Hun" and was thrilled to be able to do so. I bought a nice print of Saburo Sakai's Zero over mount Fuji, signed by the artist and Mr. Sakai, and still have it along with prints signed by Erich Hartmann and Ivan Kozhebud. All in all a wonderful evening with plenty of good memories.

 

[VBF-13]

Yah. Great movie and still is. Our museum supplied the O-47 to finish the flim when Paul Matz crashed the dedicated plane in an uneeded take. Paul died needlessly ... really an unforgivable thing. The director should be whipped but he is dead. OK.

I never knew that. And I can't get enough of that movie, too, it's a great one. Wow!

 

[GregP]

Here is the video of the Paul Mantz crash:


View: https://www.youtube.com/watch?v=n82nN_lqn58

 

[VBF-13]

Here is the video of the Paul Mantz crash:

The fuselage broke in half on the bounce. What an end to what looked like an illustrious career.

 

[GregP]

Yeah. It was a wood fuselage attached to the metal and it broke where they joined.

That is why I don't particularly like the Boeing 787 and other mixed-structure aircraft. I prefer a primary structure made of all the same material rather than a mix. I can think of two or three times when a mixed material structure broke at the interface and don't like the implications when it comes to my own neck. Call me old fashioned.

 

[J.A.W.]

The Tempest seemed to manage [tubular spaceframe to wing/stressed skin rear fuselage], as did the Mosquito [composite plywood skin/balsawood-casein sandwich matrix] `cept when used in the tropics when the glue let go-oops...Dreamliner anyone..
As for roll rate, aileron spring tabs - then servo-boosted [power ailerons] helped at higher speeds, if the wing was up to the torque demands, structurally..

 

[GregP]

I wasn't thinking of power assist surfaces when I posted above since they were so rare during WWII.

 

[Kryten]

the problem with these roll rates as far as I can see is noone has assessed just how much stick force a human being could apply?
I'm 6ft 2 and 220lb's I dont think 50lbs would be anywhere near the maximum force I could apply in that scenario?
but hang on a minute, what about when you add in g loadings, how much force can you apply when the weight of your arms has multiplied?

all seems extremely difficult to assess in reality, it will depend on who's flying it?

 

[bobbysocks]

the I-16 had one hellacious roll rate.


View: https://www.youtube.com/watch?v=jeIaVsq3DcQ

 

[GregP]

Very interesting flick. I seriously doubt the I-16 ever shot down an Me 163! And it looks like they used camera footage from all of WWII as supposed "I-16" camera film.

But the roll rate DID look pretty good though I thought the really fast rolls were snap rolls. Either way, it doesn't seem to lack for roll authority. Would love to see one of the New Zealand birds fly in person!