Bristol Bulldog Aileron

There are a few documents about spinning tests. In light of the above, this all makes sense.

Aircraftclocks, thank you. Are we talking accessible vodka drinking Cracow Museum here or inaccessible tea drinking UK museum ?

It’s the one in the UK near the famous gardens. I have always found the underground the best way to access it followed by a short walk. As to tea drinking, most likely behind closed doors as you are searched for such things on entry.

Ed-2 The comments about the various IPB’s were for your benefit.

The documents shown as being held are as follows:

AP1393A Vol. III Part I, 1931
AP1393B Vol. III Part I, 2nd edition, 1934

So looks like parts manuals for Mk I & II aircraft.

Aircraftclocks, thank you. Are we talking accessible vodka drinking Cracow Museum here or inaccessible tea drinking UK museum ?

Physics

Ed-2
The Bulldog A.P. manual calls for NO droop, and a tight cable system.

Bulldog Mk IIa Wing:
Total area (two top panels + centre section-no ailerons: 167.3 sq.ft. Aerofoil: Bristol 1A (both upper and bottom)
Ailerons (both): 24.7
Wing chord 76″
Aileron chord 23.5″
Travel: 25^ up & down

Cheers,
Ed-1

Ed1,
Tuppence worth :

Ratio of aileron to top plane on Bulldog is 1:6.7 (167.3 sq ft top plane to 24.7 aileron) in comparison to Hart family 1: 4.9 (175.46 sq ft to 35.54 aileron). Therefore the Bulldog has a more aggressive aileron, perhaps explaining its reputation as an acrobatic aircraft in the air displays of the 1930’s. The Bulldog aileron chord seems to be double that of the Hart family biplanes.

Hawker Hind has all up weight of 5217 lbs over total wing area of 348 sq ft (top and bottom planes and aileron) = wing loading of 15 lbs/sq ft.
Bulldog II has all up weight of 3503 lbs over total wing area of 306.5 sq ft = wing loading of 11.4 lbs/sq ft.

Therefore the original Bulldog had a more aggressive aileron (and I suspect tailplane arrangement) than an example of the Hart family biplane, acting on a (Bulldog) wing design (steel strip construction) of lighter wing loading. The Bulldog was a performance aircraft pushing material design limits, while the Hart family were a design with higher structural factors and less aggressive parameters (aileron travel, chord and area) helped by a powerful engine.

I believe the original Bulldog had a design fault in the provision of elevator pulleys suspended from the fuselage, in an arrangement that meant that control column forces acted as a lever on the rear elevator pulley, and material fatigue could lead to the detachment of the pulley from fuselage mounting in service. In 1937 a RAAF Bulldog was lost when it failed to recover from a dive, which might be ascribed to this cause.

http://trove.nla.gov.au/ndp/del/article/11051884

I wonder what these ratios/wing loadings are for modern acrobatic aircraft. One gentleman who grappled with lightweight aircraft structures and excessive aileron forces was Jiro Horikoshi, designer of the Zero, who introduced control cables with higher elasticity to take up some of the energy between control surfaces and control column.

There seemed to be a great degree of technology transfer between Britain and Japan in the 1920’s – 30’s, principally with the naval relationship, but also with Bristols and aircraft. I wonder how much the the affinity of Japanese designers for lightweight construction was influenced by Bristol design thought in the 20’s and 30’s. Certainly the Bulldog was built and copied by the Japanese, but maybe Jiro Horikoshi evolved a solution for lightweight structures with aggressive control surfaces that Bristols never got on top of, insisting on a tight cable system.

Ed2

Ed-1
Full scale tests of Hartshorn ailerons on a Bulldog aircraft has a former reference of B.A.1268, dated 1936 so may be a different document to R&M 1734. Only one way to find out.

Ed-2 The comments about the various IPB’s were for your benefit.

The documents shown as being held are as follows:

AP1393A Vol. III Part I, 1931
AP1393B Vol. III Part I, 2nd edition, 1934

So looks like parts manuals for Mk I & II aircraft.

The AP associated with the Appendix A, seems wrong to me, so I have started another thread on that subject to see if any information comes to hand in order to figure it out.

Ed-2
You are a wizard, sir! The Bulldog aileron is very very similar to the Hawker in profile. The spar is a bit further forward, very close to the apex of the top surface, but centered up/down. I am guessing the radius of the tip is in the 1/2″ dia.?
The bottom seems to absolutely flat. Air-clocks, I have the R&M 1734 concerning the Hartshorn aileron. Just missing the info I am looking for. The Bulldog A.P. manual calls for NO droop, and a tight cable system. Finding info on the site you mentioned has been difficult for me. Lots of titles that go nowhere. But I shall keep researching. Ed-2 thanks for the kind words of the marathon. You are wise beyond your age.
Bulldog Mk IIa Wing:
Total area (two top panels + centre section-no ailerons: 167.3 sq.ft. Aerofoil: Bristol 1A (both upper and bottom)
Ailerons (both): 24.7
Wing chord 76″
Aileron chord 23.5″
Travel: 25^ up & down

Cheers,
Ed-1

Ed
Having had a look on the public records web site there are several IPB’s available, of different editions etc. There are at least 2, Vol 3’s and an appendix A.

There is also a report on full scale tests of Hartshorn ailerons on a Bulldog aircraft.

Hawker Frise aileron

Following up on the aileron questions: I built the ailerons to follow the standard full wing rib aerofoil. The new question that comes up concerns the leading edge of the aileron, and the gap created on the up aileron. The leading edge of the aileron is rather sharp which brings up the question of aileron snatch. (I do not have a drawing of the aileron rib, thus no info on the radius of the tip, only pictures) I have a copy of the Hartshorn aileron experiment which showed very little difference between the two types. I have not been able to find info from the British side, and NACA does not address the problem in a manner that fits this aileron. (NACA keeps putting the hinge point below the aileron. The picture of the Hawker aileron is a perfect example of the Bristol construction.
So…..does anyone have info on the Hawker ailerons?

Ed,
Pictures below I trust will clear up some detail. I will send you a DXF file which should allow you to output locally a 1:1 Hawker Hart family aileron main rib as per the first picture, which are forming tools for this rib. In the photos the engagement bracket attaching rib to the aileron tube is placed, to give context to the fixing holes in the DXF file, and allow you to place the aileron tube in position. Further photos show the means of connecting the aileron tube to the ribs connecting to the spar. Between the full wing photos and these detail photos I hope there is enough for you to figure it out.

For Hart family biplanes the following data is consistent :
a) Aileron travel 22 degrees up, 18 degrees down
b) Area of top planes including ailerons 211 sq ft
c) Area of ailerons 35.54 sq ft
d) Top plane chord 6ft 0.5in, RAF 28 airfoil.

Can you tell me if the ratios of top plane area to aileron area are consistent with the above on the Bulldog, to establish, perhaps, a principle in the Frise idea of “effective working area” or “ratio of total wing chord to aileron chord”. I wonder if any of the NACA reports allude to this.

Note on the photos that the leading edge and top face of the aileron is clad across its length to give a definate and clean tip to the leading edge. The aileron is balanced with lead weights inside the leading edge, I understand that prior to this there were issues with aileron flutter.

Note on the close up of the hinge that the hinge is ‘sloppy’ within the hinging arrangement to allow for aileron function where the wing is bending in flight, a feature introduced to Sopwiths (Hawkers) in WW1. The hinge immediately adjacent to the centrally mounted aileron gearbox is, however, tight, to maintain a firm connection with this controlling means.

Just passing you a drink on your marathon,
Ed 2

PS – Are you constructing an exhaust collector ring for the Bulldog ?

Blldog and the Frise Aileron

Following up on the aileron questions: I built the ailerons to follow the standard full wing rib aerofoil. The new question that comes up concerns the leading edge of the aileron, and the gap created on the up aileron. The leading edge of the aileron is rather sharp which brings up the question of aileron snatch. (I do not have a drawing of the aileron rib, thus no info on the radius of the tip, only pictures) I have a copy of the Hartshorn aileron experiment which showed very little difference between the two types. I have not been able to find info from the British side, and NACA does not address the problem in a manner that fits this aileron. (NACA keeps putting the hinge point below the aileron. The picture of the Hawker aileron is a perfect example of the Bristol construction.

Ed-2: Bristol never used the Clark YH. The Bristol 1A and the Clark YH are very similar. The Bristol being a bit thinner. I could believe the Bristol was derived from the YH. The only aerofoils used on the Bulldog were the Bristol 1A, RAF 34, and RAF 35. (the latter two from the Mk III and IV). I have a copy of the wood wing used on the high altitude attempt, but do not know which airfoil it is. One day when I have nothing to make, I will research it.

So…..does anyone have info on the Hawker ailerons?

Thanks all.

Ed

David Luff’s Bulldog pg 57 shows a Hartshorn aileron drawing, with a tapering leading edge that results in three different rib profiles depending where the section is taken. Perhaps this explains the AP drawings showing odd shaped aileron ribs….

The problem: the depth of the Bulldog aileron on the Mk II series. Does anyone have any insight to ailerons actually being thinner than the adjoining wing? Most ailerons are either
the same size, or slightly larger than the adjoining wing. As there are no known drawings of the Mk II/IIa aileron rib all that is given is an illustration in the A.P. manual showing the
aileron slightly thinner than the wing rib. Did Bristol experiment with this idea? Bristol did one experiment with the Hartshorn aileron, but no information in that paper talks about the
original aileron. I have checked with some of the most knowledgable individuals around who were kind enough to contemplate the question. But nothing definite.
So I am hoping someone out there just happens to know, or knows who knows the answer.
Cheers

Ed

David Luff’s Bulldog pg 57 shows a Hartshorn aileron drawing, with a tapering leading edge that results in three different rib profiles depending where the section is taken. Perhaps this explains the AP drawings showing odd shaped aileron ribs….

Frise Aileron assembled in Hawker Hind wing 1936 & close up of relative dimensions between rear spar and aileron gap. Ed 2
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[ATTACH=CONFIG]224345[/ATTACH]

Frise aileron

Thank you Dave for the info and Tony for the interest. The only thing missing from the pictures would be the depth of the aileron at the tube spar. Ie. it’s thickest dimension. I have three cross sections of the
aileron at that point and they show even dimension with the wing (Mk I), and two showing the aileron thinner than the wing. (Mk II/IIa). One of them slightly thinner (10%), and the other even thinner yet.
Based on the dimension I have of the wing depth at that point (fact!), and what is shown on the A.P. cross sections, I am beginning to think the drawings in the A.P. manual are ‘illustrative’ as opposed to fact.
My wing dimension and the A.P. wing dimension (re:depth) As a point of interest, the Mk III and Mk IV wings are not the same as the Mk II’s. Completely different aerofoil. Dave, I may have to talk to you about the parts manual. Thanks everyone.
Ed

Just out of curiosity I put a Hawker Demon Frise type aileron from 1935 up against a rib to see if was thicker or thinner and Winston concurs that it exactly follows the aerofoil shape. This may just be Hawker practice or it may be that by 1935 the Frise design had settled the issue as ‘same as the aerofoil’. Why would you go thinner and perhaps set up a disturbance where there is a step down ?
[ATTACH=CONFIG]224342[/ATTACH]
[ATTACH=CONFIG]224343[/ATTACH]

I understand aerofoil on Bulldog I top main plane was Bristol 1a and this later became Clark YH on Bulldog II ? What are the aerofoil sections for the different Mks ? Do you have a copy of the Bristol 1a section ?

I would love a copy of the illustrated parts manual…..
Ed 2

The Bristol Aero Collection at Kemble had a wing from a Bulldog IIA (J3134) when I visited there in 2001. They might be able to help,
Jim

Few guesses

The problem: the depth of the Bulldog aileron on the Mk II series. Does anyone have any insight to ailerons actually being thinner than the adjoining wing? Most ailerons are either
the same size, or slightly larger than the adjoining wing. As there are no known drawings of the Mk II/IIa aileron rib all that is given is an illustration in the A.P. manual showing the
aileron slightly thinner than the wing rib. Did Bristol experiment with this idea? Bristol did one experiment with the Hartshorn aileron, but no information in that paper talks about the
original aileron. I have checked with some of the most knowledgable individuals around who were kind enough to contemplate the question. But nothing definite.
So I am hoping someone out there just happens to know, or knows who knows the answer.
Cheers

Ed

A few guesses :

1. Bulldog II sent to US Navy for testing in 1930 crashed when aileron failed in terminal velocity dive. “tests at Filton resulted in a modification and a replacement was shipped in February 1930” – Bristol Bulldog, A Granger 1973
and
“The Bureau of Naval Aeronautics placed an order for a Mark II in order to evaluate it at Anacostia Naval Air Station…given registration A8485..on 25 Nov it experienced aileron flutter in a terminal velocity dive and crashed….This was the first fatal accident due to aileron flutter on a Bulldog and no doubt much heart searching took place at Filton. Modifications to wing and aileron spars were quickly incorporated after static testing of the wing structure…a replacement aircraft A8607 was used to continue the evaluation trials before being struck off charge on 27th August 1931…the airframe was tested to destruction, results shared with manufacturers and RAF.” – Bulldog, David Luff, pg 120

So perhaps the US Navy will have some records that shed light on Bulldog II ailerons.

NACA has some wind tunnel tests on the Frise type ailerons originated by Leslie Frise at Bristols.
NACA TR 422, Slotted ailerons and Frise ailerons, 1932

Bristol’s thought processes might be apparent in this excerpt from trade literature for Bulldog IIA which I believe was printed around the time of the US Navy experience :

“Flying qualities.The degree of balance and amount of shielding has been carefully decided upon, after model and full scale work, to give a light control at all speeds and yet prevent any suggestion of hunting or flutter in a terminal nose dive”

Given this it is plausible that Leslie Frise, on the staff of Bristols, was probably the most qualified person on the planet to experiment with his Frise aileron designs, and given this design would have been a trade advantage in the highly competitive world of aircraft sales in the Depression, it would also seem plausible that improvements were not documented for the benefit of competitors.

I would trust that the APs, in the sense that they ‘cut and pasted’ manufacturers drawings, do indicate that there is a change in aileron designs, and in the context of the US Navy experience and Frise being employed at Bristols, eliminating aileron flutter drove evolutions in the design.

Dimensions ? Ha ! Maybe chalk the aerofoil on the floor and place the tail of the known aileron at the tail of the aerofoil to figure if gap between wing and aileron was one of the changes. My understanding is that the Frise aileron followed the aerofoil section and what is implied by a thinner aileron is a different aerofoil for the aileron ? Maybe reference to later Bristol designs or other aircraft using Frise ailerons will indicate whether the concept of ‘thinner’ ailerons travelled through. There are some further NACA reports on Frise type ailerons in 1941-2 that may have been prompted by evolutions in the design.

Machining up oil cooler segments now, lots of pieces, all in good time,
Ed

Thank you Dave for the info and Tony for the interest. The only thing missing from the pictures would be the depth of the aileron at the tube spar. Ie. it’s thickest dimension. I have three cross sections of the
aileron at that point and they show even dimension with the wing (Mk I), and two showing the aileron thinner than the wing. (Mk II/IIa). One of them slightly thinner (10%), and the other even thinner yet.
Based on the dimension I have of the wing depth at that point (fact!), and what is shown on the A.P. cross sections, I am beginning to think the drawings in the A.P. manual are ‘illustrative’ as opposed to fact.
My wing dimension and the A.P. wing dimension (re:depth) As a point of interest, the Mk III and Mk IV wings are not the same as the Mk II’s. Completely different aerofoil. Dave, I may have to talk to you about the parts manual. Thanks everyone.
Ed

Ken this is a Bristol Bulldog http://en.wikipedia.org/wiki/Bristol_Bulldog not a Scottish Aviation one.

Can I suggest you give Martin Jones a ring at Derby Aero club as they have lots of info and do loads of work on Beagle Pups and have modded a few Bulldogs to civilian specs, plus there are a couple on site. number is 01283733803

I don’t know if this is of any help?

Dave