Boosted ailerons on Fw 190D-13

[spicmart]

Some sources mention hydraulically boosted ailerons on the existing Fw 190D-13. Others don't mention anything.
Then I read a source that says that the Dora got outrolled by a P-38 with boosted ailerons indicating that the Fw does not have those.
Otherwise it would have rolled faster than the P-38 due to the much smaller surfaces.
Does anybody know more about it?

 

[stona]

The famously restored D-13 'Yellow 10' was originally fitted with the 'wrong' wings from a D-9 and as a result a small access panel in the wing root for the hydraulic aileron boost was blanked off. 'Yellow 10' now has the correct wings.

On 7th April 1945 just TWO D-13s were in service. It is possible that as many as seventeen were built. Any comparison with a P-38 cannot be with a D-13, but more likely a D-9 which did not have boosted ailerons.

Cheers

Steve

 

[spicmart]

Then the D-13 would have outrolled pretty much anything.

 

[GregP]

Not necessarily. Boost does not mean better roll, it means less effort for the same aileron deflection. If the pilot was strong enough to get full deflection anyway, it won't roll any faster; it will just take less effort.

Though comparative testing would have to be established to confirm it, it is probable that boosted ailerons would roll at least somewhat faster. With only a handful ever completed, we will probably never know for sure.

 

[stona]

I don't know if the Germans ever did a comparison between the roll rate of a D-13 (boosted) and a D-9. Probably, but I've never seen it.
Cheers
Steve

 

[tomo pauk]

Not necessarily. Boost does not mean better roll, it means less effort for the same aileron deflection. If the pilot was strong enough to get full deflection anyway, it won't roll any faster; it will just take less effort.

Though comparative testing would have to be established to confirm it, it is probable that boosted ailerons would roll at least somewhat faster. With only a handful ever completed, we will probably never know for sure.

Once the speeds became too fast for the pilots to apply a needed stick force, the boosted ailerons were very much needed. In other words, at speeds above 350-400 mph, the capability of the aileron became greater than pilot's capability to do the maximum aileron 'throw' - the aerodynamic forces were simply to high.
Of course, the bigger aircraft with bigger ailerons needed boosted ailerons at much lower speeds.

 

[stona]

Using boosted ailerons to achieve large or maximum aileron movement at high speeds might also have unanticipated consequences for the wing as a whole. It is not neccessarily a simple solution to the inability of the pilot to apply enough force to the control input.
Cheers
Steve

 

[GregP]

Aeroelasticity could rear its ugly head, for sure. That wasn't the case for the P-38J-25 and later Lightnings, but I've heard it could surface in the late moel Spitfires. The Fw 190 series, though really good rollers at lower to medium speeds, began slowing down in roll as it approached 400 mph and, much above that speed, was out-rolled by a numnber of fighters.

The thing to remember is that while they could GET to 400 mph, it wasn't a frequent occurrence, so the net experience at very high speeds was rather low and I don't believe there was much of an effort to communicate flight characteristics at higher speeds to the pilot community in general, other than the pilot's manual, which probably wasn't read very often after a pilot became somewhat familiar with his mount.

The Bf 109, in particular, had control surfaces that got VERY stiff at higher speeds. Above 400 mph the stick felt like it was set in concrete according to several books and interviews with 109 pilots. Several went straight into the ground out of high-speed dives from which recovery was impossible. I have often wondered how it might have fared had it been equipped with boosted controls, including the elevator and rudder. But, since Messerschmitt never even got around to rudder trim, the likelihood of a boosted rudder would seem to be almost negligible. Still, it might have made the Bf 109 into much more of a high-speed contender.

 

[BiffF15]

Not necessarily. Boost does not mean better roll, it means less effort for the same aileron deflection. If the pilot was strong enough to get full deflection anyway, it won't roll any faster; it will just take less effort.QUOTE]

Greg,
Actually boosted ailerons mean the plane will roll quicker "initially", just not sustained. What's important in a fight is to have a quick roll rate to avoid lead poisoning (a quick roll and pull to get out of the way), with rolls usually being 180 degrees or less. The boost didn't help with sustained rolls, but it would help in a twisting turning fight. Obviously this is my opine and an extrapolation from current to past!
Cheers,
Biff

 

[GregP]

Hi Biff,

I don't categorically disagree, but if the pilot is strong enough to be able to apply full deflection rather rapidly, then I doubt boost will improve anything much. If the pilot is NOT strong enough to apply full deflection, as in a Bf 109 at high speed attempting a roll then yes, boost will increase the initial roll rate as well as the sustained roll rate.

If the boost helps him apply full deflection noticeably quicker but he can get to fuill deflection, then yes, it will improve initial roll rate but not the sustained roll rate.

In WWII we probably had many planes that could have used boost and never got it. We all know the P-38J-25 and later Lightnings got aileron boost and it improved their roll rate because few people were strong enough to 350+ mph to get rapid fuill deflection.

I wish we had test results of the purported Fw 190D-13 boost test bed.

 

[tomo pauk]

The roll chart for the P-38J with boosted ailerons. Above 200 mph IAS the pilot was unable to fully deflect the ailerons in case the boost was not used. Even at relatively low indicated speeds (100-250 mph) the time to perform a 90 deg bank was cut between 2 to 3 times! Of course, having the heavy items away from the centerline meant that the non-boost roll rate was abysmal to start with.

http://www.wwiiaircraftperformance.org/p-38/p-38j-roll.jpg

Using boosted ailerons to achieve large or maximum aileron movement at high speeds might also have unanticipated consequences for the wing as a whole. It is not neccessarily a simple solution to the inability of the pilot to apply enough force to the control input.
Cheers
Steve

Not all the wings were created equal. The wing of the Fw 190 was regarded as a pretty strong item IIRC.

 

[GregP]

I believe the Fw 190 did aileron rolls that would have ripped the wings from most other fighters. Strong wing on the Fw? I'd say very much so.

Now the long wings of teh Ta-152, I don;t know. You'll NEVERE get a long , narrow0chord wing to roll as quickly as a shorten, wider-chord wing. I do not know the relative strength of the Ta-152H wing, but the Ta-152C wing was pretty much the same as a Dora wing.

 

[BiffF15]

Hi Biff,

I don't categorically disagree, but if the pilot is strong enough to be able to apply full deflection rather rapidly, then I doubt boost will improve anything much. If the pilot is NOT strong enough to apply full deflection, as in a Bf 109 at high speed attempting a roll then yes, boost will increase the initial roll rate as well as the sustained roll rate.

If the boost helps him apply full deflection noticeably quicker but he can get to fuill deflection, then yes, it will improve initial roll rate but not the sustained roll rate.

In WWII we probably had many planes that could have used boost and never got it. We all know the P-38J-25 and later Lightnings got aileron boost and it improved their roll rate because few people were strong enough to 350+ mph to get rapid fuill deflection.

I wish we had test results of the purported Fw 190D-13 boost test bed.

Greg,
We are on the same boat. My point (and not well typed) is that you don't want to have to be a strong pilot or put a tremendous amount of physical effort into something in the middle of a fight. It requires too much concentration / effort and reduces the ability to fight and fight well.
Cheers,
Biff

 

[GregP]

Agreed and I think boost on all surfaces would have helped ALL the WWII fighters. It well might have also exposed some aseroelasticity at high speeds and could have driven some of the existing desgns into aileron reversal. I have heard the Spitfire wings were not as torsionally stiff as they desired, and going to metal-covered ailerons and boost may have caused a problem nobody wanted to address.

At sufficiently high speeds, that could have been the case for almost ANY of them. In point of fact, the P-38J-25 and onward got boost only for the ailerons and I am not aware of a fully-boosted WWII piston fighter. I do not know off the top of my head whether the early jets were manual, partially boosted, or fully boosted. We all know that fully boosted control became the standard eventually.

 

[stona]

The Me 262 did not feature any boosted flying controls.

Cheers

Steve

 

[stona]

The Me 262 did not feature any boosted flying controls.

Cheers

Steve

 

[GregP]

Thanks, Steve!

I'll check on the P-80 next weekend and report. The subject just never came up for me before. The planes I have been working on are all unboosted and I never worked on flight control surfaces on an F-86. Just leading edges, flap structure, landing gear, and wing attach areas.

We have a Meteor III at the Museum, but it is a shell with almost no equipment in it. Still, the guys at Fighter Rebuilder will very probably know about the Meteor.

 

[FLYBOYJ]

P 255 of the F-80 mm (TO 1F-80A-2) explains the system

 

[GregP]

Thanks Joe!

 

[Koopernic]

The Me 262 did not feature any boosted flying controls.

Cheers

Steve

However the Me 262 did feature spring servo tabs to reduce pilot effort. In these the ailerons feature small tabs that are rigged directly to the pilots joystick to deflect in the opposite direction so as to indirectly deflect the aileron. The ailerons were still deflected directly by springs.

We have a roll rate from Eric Browns test flights:
"The normal range of flight characteristics from aerobatic manoeuvres to the stall revealed the Me 262 as a very responsive and docile aeroplane, leaving one with a confident impression of a first class combat aircraft for both fighter and ground attack roles. Harmony of controls was pleasant, with a stick force per 'g' of 2.72 kg (6lb) at mid-CG position and a roll rate of 360 degrees in 3.8 seconds at 645 km/h (400 mph) at 1525m (5000 ft)."

This 94 degree a second roll rate exceeds every Allied and German piston fighter at 400mph and above including fast rolling aircraft such as the P-51B, Clipped wing spitfire, P-63 King cobra ( fastest rolling US aircraft) and Fw 190.

The Spitfire F.22 did feature something similar: "Balance Tabs" on the ailerons which lack the springs.
And of course some Me 109G built by WNF featured them as well as likely some Me 109K.

So there are ways of reducing aileron force without boosting with hydraulics.
1 Flettner Tabs: small tabs are deflected by the controls thereby deflecting the aileron, rudder, elevator. Named after the famous German inventor Anton Flettner. Often just called servo tabs.
2 Balance Tabs. The tab and the aileron are locked in a fixed ratio. Since these become over effective at high speed the can have only limited deflection.
3 Spring Tabs, like Flettner or servo tabs, however springs also help deflect the surface. In German and European countries just called Flettners as he patented these also.
4 Geared Spring Tabs the tabs deflection is reduced at high speed to avoid over control, developed by the NACA and used in late war USN fighters like the Hellcat and Corsair to greatly increase roll rate.
5 Internal Pressure balancing, used on the P-51 whose laminar profile wing was thick enough to accommodate the system. Pressure from the deflected aileron is channelled to a sort of below to reduce the force needed.
6 Horn balance, seen on rudders, a forward protruding surface ahead of the hinge. Causes a Mach problem, late war Me 109 had a tall tail that replaced the horn balance greatlyu increased dive speed.
7 Friese ailerons, slight protuberance on aileron to reduce workload, causes mach issue but not nearly so much as horn balance. Very common. Fw 190, metal aileron Spitfire V, Me 109F onwards.

Spring tabs could control the B-36 and Boeing 707 but can get into trouble with flutter or over control at high speed unless carefully designed.

The only German aircraft I know had fully boosted controls was the Do 335. The Fw 190D-13, He 162 maybe Ju 290 may have had them or had plans for them. The Germans thought it likely they would need them for their next generation swept wing aircraft, according to "Secret Messerschmitt Projects"