Fw-190: the roots of the great roll rate?

[riacrato]

I cannot say, but 190 wasn't the only plane with one piece wing, for ex Brewster Buffalo had one and that structure had also its drawbacks, at least that was the opinion of S/L Churchill in his assestment on Brewster Buffalo as a combat plane. He was the leader of the Eagle sqn (RAF 71 Squadron) consisting American volunteer pilots. They were given three Brewsters, which must also have been 339Bs. He filed this report in October 1940.

"It is strongly recommended that this type should on no account be considered as a fighter without considerable modification.

The wings are not bolted to a centre section but appear to have a common main rear spar located through the fuselage. Changing wings in the event of accidents will therefore be uneconomical and slow.

The elevator is actuated by a push-pull tube. While this is a positive method of operation it is feared than an explosive shell or even a bullet . . . may shatter or collapse it. Experience has proved how much punishment the twin cable can stand without breaking down..."

So even the push-pull tube had its downside.

Not really enough to convince me that this fear really materializes in reality.

And as has wrote earlier 190 lost its lead in high speed, P-51B rolled better at 360+mph IAS and Tempest V at 365+mph IAS at 10000ft.

Juha

Which I always thought was due to the fabric covered aileron surfaces. Metal skinned elevators might have enabled the Fw 190 to keep its edge, but the question is if it was worth the trouble (and material).

 

[Vincenzo]

i've used this True Airspeed Calculator

 

[drgondog]

i've used this True Airspeed Calculator

It uses one of the 5 Rule of Thumb calculations - Calculate your True Airspeed (TAS) [Aviation Rules of Thumb] - Flightsim Aviation Zone

From the same chart (My "Altitude vs True Airspeed" plots) I get 194Kts for the same calc as your link. BTW, the link calc is incorrect in that they used "8.0" for 8500/1000 when he reduced the equation to (.02 x 8) when he should have used (.02x8.5) x 170. The correct calculation would have been 198.9.

All these methods have the drawback of variations depending on Mach number, calibration deviations, surface pressure/temperature. For the Mustang calc, the incompressible flow became compressible at ~ .3M (or for STP at 10,000 feet =218.36 mph) - which is why I try to use the 'Book' Altitude vs True Airspeed - which is corrected for Mach number.

 

[rinkol]

It might be noted that, all other things being equal, that the fighters with wing mounted radiators tended to suffer from the loss in torsional stiffness resulting from the needed cutouts in the wing skin.

 

[stona]

Not possible without access to the airframe design/structures analysis - unless you want to start from scratch using the detail design and BOM, the Aero loads as calculated and presented to the structures group.

Yes,but that transference would explain why the rear spar is often referred to as auxiliary or secondary and also why many seem to consider the wing to have been a single spar design.
Steve

 

[drgondog]

Yes,but that transference would explain why the rear spar is often referred to as auxiliary or secondary and also why many seem to consider the wing to have been a single spar design.
Steve

A 'spar' is a structural member capable of resisting bending loads, a spar integrated with other structure as well as 'skin' is capable of Bending and Shear resistance. While a spar may be primary, and another secondary, they will serve essentially the same purpose although the secondary is by definition the lesser of the two structural systems.

In airframe design, it is rare for an aircraft with training edge control surfaces to Not have a beam we may describe as 'secondary'.

 

[Vincenzo]

It uses one of the 5 Rule of Thumb calculations - Calculate your True Airspeed (TAS) [Aviation Rules of Thumb] - Flightsim Aviation Zone

From the same chart (My "Altitude vs True Airspeed" plots) I get 194Kts for the same calc as your link. BTW, the link calc is incorrect in that they used "8.0" for 8500/1000 when he reduced the equation to (.02 x 8) when he should have used (.02x8.5) x 170. The correct calculation would have been 198.9.

All these methods have the drawback of variations depending on Mach number, calibration deviations, surface pressure/temperature. For the Mustang calc, the incompressible flow became compressible at ~ .3M (or for STP at 10,000 feet =218.36 mph) - which is why I try to use the 'Book' Altitude vs True Airspeed - which is corrected for Mach number.

the example is incorrect but for us is ok 360+7,2*10 is 432, it's same of number 3 in your link and yes is the highest estimation (n° 1 and 2 give 410)

 

[drgondog]

the example is incorrect but for us is ok 360+7,2*10 is 432, it's same of number 3 in your link and yes is the highest estimation (n° 1 and 2 give 410)

And it is Wrong by a significant amount.

 

[cimmex]

432mph or 410mph, I doubt that the P-51 or Fw190 could achieve this speed at 10000 feet at all.
cimmex

 

[Juha]

Hello Vincenzo
I used the info from a table tabulated by the Kingston (Hawker) Project Office 1964 which was given to me years ago by an ex-Hawker wing specialist.

Juha

 

[Juha]

432mph or 410mph, I doubt that the P-51 or Fw190 could achieve this speed at 10000 feet at all.
cimmex

IMHO in dive or after a dive, so possible in combat but not usual combat speed.

Juha

 

[Juha]

Not really enough to convince me that this fear really materializes in reality...

Hello riacrato
I'm not trying to convince anyone, I included that part mostly to hint that S/L Churchill might has been a bit conservative in his opinions on a/c structures and systems and also that a/c design decisions were usually based on compromises. Especially when it is question on mass produced types.

Juha

 

[Juha]

The writer of the Flight article to which I posted link earlier wasn't an average engineer but one of the bright stars of the trade, see: Robert Lickley - Wikipedia, the free encyclopedia or better still Aircraft Designers Engineers and Notables: Sir Robert L.Lickley CBE 1912–1998 , so he probably knew the subject well. If he categorized Spitfire wing as an one spar structure it's enough to me.

Juha

 

[tomo pauk]

Sea Fury - 2 or 3 spars? The photo the the left is from Seafire, another is from Sea Fury.

 

[drgondog]

Sea Fury - 2 or 3 spars? The photo the the left is from Seafire, another is from Sea Fury.

View attachment 215568

I could easily argue three.

 

[tomo pauk]

Even better photos of Seafire wing fold; you can easily navigate to another detailed photos (Sea Fury included):

Seafire Mk XV wing fold detail photos

 

[stona]

In airframe design, it is rare for an aircraft with training edge control surfaces to Not have a beam we may describe as 'secondary'.

By which definition no aircraft built with trailing edge control surfaces can be a single spar design. I don't believe that to be the case. There are too many references by engineers and designers to single spar wings that do have moveable control surfaces attached to the wing trailing edge. It may just be semantics or a question of degree. If the vast majority (pick a figure ) of the loads are borne by the mainspar then this might be considered a single spar design.

Cheers

Steve

 

[Timppa]

Sea Fury - 2 or 3 spars? The photo the the left is from Seafire, another is from Sea Fury.

View attachment 215568

Seafire 1 spar, Sea Fury 2 spars. All the forces must go through the locking eyes.

 

[drgondog]

By which definition no aircraft built with trailing edge control surfaces can be a single spar design. I don't believe that to be the case. There are too many references by engineers and designers to single spar wings that do have moveable control surfaces attached to the wing trailing edge. It may just be semantics or a question of degree. If the vast majority (pick a figure ) of the loads are borne by the mainspar then this might be considered a single spar design.

Cheers

Steve

Steve, as an airframe structures guy in my youth I can regurgitate the primary approach. First the main spar would be (Should be) close to the aerodynamic center of pressure as possible to be The beam to take all or most of the bending loads due to span and chordwise distributed loads. You may call it what you wish. Other engineers may not parse the phrase the way I do. Having said this I am pretty familiar with the SR-71 and the Bell XV-15 (precursor to V-22) and I can assure you the rear structure, upon which were hung a variety of control surfaces, were essential in both bending and torsion considerations.
If you wish to consider examples of designing a trailing spar, upon which to hang articulated flap shaft bearings on a wing subjected to EXTREME bending loads and wing deflection on jump take off - look to the Bell XV-15 and V-22 and Vought XC-142 (?CRS).

Net - I choose to parse the phrase and will stick to my considered opinion regarding what 'constitutes', and may be defined as, a beam or a spar. We may agree on the primary load bearing member, and I am happy to agree that it may be called a Single Spar - but I don't agree it is the only 'spar', nor is the trailing edge the Only bending load carring member as leading edges also served that purpose - particularly in torque/torsion deflection calcs.

 

[drgondog]

Seafire 1 spar, Sea Fury 2 spars. All the forces must go through the locking eyes.

Timppa - basically true for one flight condition. All the forces outboard of the locking eye rib/wing station must go through the locking eyes. The majority of the symmetrical aero loads will be in the first 50% of the semi span, the outer span will have some aero laods but the primary load transfer should be from the ailerons in high speed asymmetric rolling..