Aircraft Control Surface Balances

Gentlemen All,
I thank you for your explanations as to why mass balances were needed, and used. A little bit more aviationeering understood! You will remember, though, in my original post that I said I was very interested in what materials might have been (or are!) used. I didn’t want to pre-empt any reply but the several separate mentions of Depleted Uranium has, I think, solved the problem.
Shortly after Chernobyl the UK Govt decided to set up a country-wide network of radiation monitoring stations. Quite a lot of these were on airfields (civil and military). One was installed in the middle of a fairly busy airport in the Midlands. After about a year’s worth of data had been recorded it was noticed that there were some persistent ‘spikes’ in the radiation levels above the normal background (not high enough to trigger the alarm threshold!). I was asked to investigate this. The data were analysed. All sorts of tricks were used. Did the spikes co-incide with the operation of any electrical equipment? (We’d had a radio controlled camera filming a Harrier test which kept firing off “random” frames. This was eventually traced to opening/closing the fridge door in the transport cafe in who’s car park we were working!!! – so you can’t be too careful!). No correlation. Did the spikes occur when it rained/thundered/hailed/ATC radio, etc, etc,? – no correlation. Finally, in despair, I plotted the spikes against wind direction – BINGO! They all came from 3 distinct directions – and were persistent. Half a mile to the NW of this airfield is a manufacturing facility. There were spikes when the wind blew from this direction. One mile to the SW is a similar facility – ditto. But, the third ‘spike’ direction was from the SE. No immediately observable industrial process there – except the aircraft handling apron!!! I think, Gentlemen, you may have solved a conundrum that has been bugging me for years. Thank you.
I have, by the way, no knowledge if the radiation monitor is still there, or which Govt Dept is now responsible for correlating the data. The Met Office had the monitors on a number of its sites, but simply passed the data on. The Home Office (Civil Defence lot) did a lot of work, but when they were done away with I have no idea where the figures went .
My thanks again
Resmoroh

Flutter was a relative unknown in the 1920s, though it is suggested that it was the introduction of the stiffer metal airframes that made it more of a killer. The first understanding came as a result of the crashes of the Parnall Pipit in 1928 and 1929, which were studied by the Flutter Sub Committee of the Aeronautical Reseach Council, leading to the issue of R&M 1247, Tail Flutter of a Particular Aeroplane, May 1930, Duncan and Collar. This was followed by R&M1225, The Flutter of Monoplanes, Biplanes and Tail Units, 1931, Frazer and Duncan.

An account is summarised in Putnams’ Parnall Aircraft, Ken Wixey, but otherwise you’d have to go to University or aircraft company Libraries to track down the reports. Just one example of how the advance of aviation was achieved by scientists and engineers in government-based organisations, rather than purely by commercial companies. Something that tends to be overlooked or even derided nowadays.

So we are talking mass (weight) balancing instead of aerodynamic balancing such as the rudders of aircraft like the Fokkers, Nieuports, Avros etc. Seems a rather thin dividing line as the former seems to be a development of the latter.

C-130 Elevators had DU although I believe that they are being phased out. Most British ac I’ve come across seem to have used common or garden lead

The stretched C-130’s have DU for elevator balance weights, while the shorter, non stretched aircraft have lead.

Q1 When were these counterbalance masses first used?
Q2 What substances were used as counterbalance weights in civil aircraft from the mid-80’s onwards.
Resmoroh

Gents…Res was quite clearly asking about Mass balance and when it was first used !!
Aerodynamic and pressure balancing are fitted for a very different reason and i think it is overcomplicating a very simple question.
Mass balance is very simply a weight (or weights) mounted forward of the control surface hinge line to bring the centre of gravity of the surface forward of the hinge line thereby preventing flutter.
So does anybody know when mass balancing was first used ??

regards baz

The earliest aircraft I can think of are the Fokker D.VII and Sopwith Snipe, which both had aerodynamically balanced ailerons.

The Fokker E.III had a balanced rudder? – before that the Avro 504? – and even earlier the Bleriot XI elevators are sort of balanced (though I don’t know if that was what Bleriot intended)

Roger Smith.

[QUOTE=Lindy’s Lad;1331708]’Depends on the aircraft’ is the rather veiled answer!

There is also a balance method which utilises differences in pressure to assist the balance of the control surfaces – a plate extends forward of the control surface into the aerofoil section and is acted upon by the differing pressures above and below the aerofoil. Moving the control surface alters these pressures which in turn assist the movement of the control surface.

Something like this…….

The earliest aircraft I can think of are the Fokker D.VII and Sopwith Snipe, which both had aerodynamically balanced ailerons.

C-130 Elevators had DU although I believe that they are being phased out. Most British ac I’ve come across seem to have used common or garden lead

Res – you described a ‘mass balance’ very well. Lindy’s lad added the description of an ‘aerodynamic balance’. While (I understand) they provide a balance to mean that the control surface moves easily without extra force being required to turn them, the main requirement is to ensure they stop the onset of flutter – which was often fatal.

I think, from recollection, they became common in the 1920s (the mass type first) certainly by the 1930s they were pretty standard – happy to be corrected.

With ailerons, there’s also the question of differential aileron movement and items like Frise ailerons or shrouded ailerons to ensure the drag doesn’t overcome the required turn, causing adverse yaw…

I was under the impression that at least some versions of the 74 had tail surfaces fitted with amounts of depleted unanium – or some other such dense material… but I may be wrong!

The 747 and the Tristar had depleated uranium used in certain parts of the flying controls. As for other modern transport aircraft, I don’t know.
Depleated uranium is SUPOSEDLY safe un less you start drilling or cutting it. There are stories of scrap depeated uranium mass ballences being cut up and used as rivet “Bucking bars” due to them being very heavy for their size:eek:

Rgds Cking

The horn balance of a Mk XIV Spitfire rudder, (the green section) being made of lead.

Similar weights on the Messerschmitt 109, these made of cast iron. ‘Fine balancing’ of these acheived by drilling holes in them to lighten them. If more weight required, holes again drilled and filled with lead.

Chumpy.

Lindys Lad
You appear to be rather overcomplicating the issue,does not matter where or how the weight is attached…it still does the same job !!

regards baz

Modern airliners do not use mass balances like this –
😀

I was under the impression that at least some versions of the 74 had tail surfaces fitted with amounts of depleted unanium – or some other such dense material… but I may be wrong!

‘Depends on the aircraft’ is the rather veiled answer!

Aircraft like the P-38 had a mass balance which was fixed to the outside of the control surface – in the P38’s case the best example is on the elevator. A lead based weight supported above and forward of the hinge line.

Steel is more common now for this type of balance, HOWEVER this type of balance has long been superceded…

Another type of mass balance can be bolted directly to the control surface, again forward of the hinge piont, but with minimal aerodynamic loss – it is shielded from the airflow by the fixed aerofoil.

There is also a balance method which utilises differences in pressure to assist the balance of the control surfaces – a plate extends forward of the control surface into the aerofoil section and is acted upon by the differing pressures above and below the aerofoil. Moving the control surface alters these pressures which in turn assist the movement of the control surface.

Movement assistance can be given by extending the control surface forward so the when the surface is moved, the leading edge sticks out into the airflow in the opposite sence to the main part of the surface.

Balance horns work in the same way as the above – think Spitfire rudders…

Here endeth the history lesson…

Now then, modern stuff! The internal mass balances you refer to, again depends on the aircraft type. The internal balances are not designed to be removable components (They can be removed, but are a nightmare to do! Its easier to change the surface). Often lead or steel based, but dependant on the size of the surface can just be milled aluminium. Corrosion is not an issue as they are heavily coated in JC5 or equivalent jointing compound, (PRC, etc). Reading between the lines, I can see an arguement for more hazardous substances, but the extremely dense usually radiocative materials, are overkill for the job.

Modern airliners do not use mass balances like this – the use of powered flying controls has negated the use of balances.

As for when… pass.

😀

Q1 When were these counterbalance masses first used?

Resmoroh

Mass balance weghts are fitted to prevent control flutter by moving the control surface centre of gravity forward of the hinge line,and they were certainly in use before the Aeronca type ‘L’ as pictured below (external balance weight)
cheers baz

Q2 What substances were used as counterbalance weights in civil aircraft from the mid-80’s onwards.
Resmoroh

I believe depleted uranium was used on some surfaces as mass-balances