Brakes Off!

[noisy]

I was sat in a spamcan with my instructor last Saturday at EGTR. We were queuing for fuel behind the Chipmunk. My instructor turned to me and said “Of course, the reason we have the ‘Brakes Off’ part of the check is because of the Chipmunk…It’s brakes are hand operated.”

I am aware that many classic British types esp. military a/c have a hand operated brake with differential control through the rudder pedals.

Which was the first aircraft to be so-equipped? It wasn’t the chippy.

[LowNSlow]

Gladiator maybe? If not, then the Hurricane?

[TD&H]

And the last type? Didn't I read somewhere that the Lightning (EE) had (has) hand operated brakes??? I like this way of braking.

[noisy]

Dunno If the gladiator has brakes at all-I will have a look the next time I go to the Battle of Britain hall (if I remember). Some canadian Tiger Moths have brakes but I don't know if these are original fit.

[Shaggy Sheep Driver]

The Chippy's brakes aren't so much hand operated, as hand selected and foot operated (through the rudder bar, as you say). The Yak 52, on the other hand, is foot selected (through the rudder bar) then hand operated (through a stick-mounted brake lever). Two quite different braking techniques.

On the Chippy, you 'set' the brake lever by hand, and apply the brakes with the rudder (re-adjusting the hand lever as and when required). On the yak, you 'rudder' in the direction you wish to turn, then apply lots of small hand brake applications (hiss, hiss, hiss, hiss). Except when it's muddy and the brakes are ineffective. Then, power on digs the RH main wheel in and you turn right, and sudden power off digs in the left and you go that way:)

The Viscount also had hand-operated brakes, as I observed during my one and only jump seat ride on type (actually it was 'stand behind the P2' ride - there was no jumpseat;) ).

BTW what is significant about brakes off at the pumps and hand-operated Chippy brakes? I though it was so you could push aeroplanes out of the way in the event of fire.

SSD

[DragonflyDH90]

As far as this brake system goes back Im not to sure, but three aircraft I fly (the DH83 Foxmoth, DH90 Dragonfly, and the DH89 Dragon Rapide) all have a similar arrangement to the "Chippie".

A very user friendly system once you get used to it, its not some much an aid to stopping, more for enhanced taxying (especially in wind) and to give you a bit more directional control in initial take-off and landing roll (with a couple of notches selected for differential braking).

Works well.

All of these types were designed and built in the early to mid 1930's so I presume this system came into vogue around this time.

[LOMCEVAK]

The Lightning definitely had the brake handle on the stick and was, I believe, the last British aircraft that had this braking system. The Hurricane is the earliest type with this configuration that I have encountered, although there probably were earlier types.

The way in which it works is that a brake application with neutral rudder results in equal brake presure to both main wheels. Full rudder with brake gives brake pressure to only the wheel on the side of the applied rudder (the normal technique for turning whilst taxying). Partial rudder with brake gives differential brake pressure.

I consider that there are two weaknesses with this system. Firstly, it increases the ground roll during crosswind landings. Secondly, you have to keep one hand on the stick in order to turn or slow down whilst taxying. The strong point for this type of brake system was that it was fitted to some fantastic aircraft (Spitfire, Hunter, Lightning etc)!

[Scion]

Dragonfly,
I am interested in the differances you may find in flying the DH90 and the DH89 .

I fly a DH 89 in Sydney and find it a delightful aeroplane to fly.

However another aeroplane I fly in decending turns will want to roll out of the turn but the DH 89 will want to tighten the turn.

Have you noticed this and is it a DH trait? or is my rapide badly rigged?

At any rate the brake lever gives you something to pull on when the end of the strip comes inexorably closer, it doesn't do a lot and it should not as you will be in a most unfortunate position if the tail goes up but you can enjoy pulling on it!

[Airbedane]

The Hind and Gladiator both have brake levers, so the Hurricane wasn't the earliest.

Regarding spiral stability, Scion, it's all to do with: dihedral, incidence, lift co-efs, wing inertia, roll damping, aileron position, fin/rudder effectiveness, aispeed and maybe a few other things I've forgoten. Whichever one wins will cause either neutral (stays where it is), positive (rolls out) or negative (rolls in) stability. Different aicraft of the same type will exhibit different characterisics, even if rigged to spec, so I don't think there is anything wrong with your machine.

[John Farley]

Scion.

Many aircraft have very weak spiral stability. Next time you fly anything in fairly calm air, trim it out straight and level as carefully as possible making sure that the ball is also centred. Then apply a little aileron and release the controls without centring the wheel/stick. Observe whether it rolls in or out (a small beer that it rolls in). If it does roll out (very unlikely) you have a powerfully spirally stable aeroplane and can talk about it as such. If on the other hand it rolls in you do not know (yet) whether it is stable or unstable. Repeat the test again (as before) but this time make a final small aileron input towards wings level and then release the controls. If it now rolls out then your aeroplane is probably as near neutrally stable as matters and what you are observing is not spiral instability/stability but an aileron driven rate of roll due to friction in the control runs than prevents the exact centring of the ailerons on release.

From the above you will see that it is very hard to measure the sign of spiral stability without having a means in the cockpit to ensure that the ailerons are exactly centre when you let go of the controls.

For some years I regularly flew aero eng undergrads in a PA44 to introduce them to a few facts of life. They knew all about spiral instability (naturally) so when after releasing the controls in a 30 deg bank turn three times on the trot and they always saw it roll in they confidently declared the aircraft unstable. But as you would guess I then did it one more time. Hopefully they will remember for good that control friction can be an issue when measuring stick free spiral stability.

[LOMCEVAK]

Scion,

Following on from what John Farley has said, if an aircraft exhibits positive lateral static stability, the technique for evaluating the spiral mode is usually to use rudder to roll to 20 deg bank, stabilise, then release the rudder. This negates any friction problems in the lateral control circuit. It is quantified as the time to half or double amplitude (10 or 40 deg bank). Note that you may need some back stick to stop the nose dropping. If you have an aircraft with neutal lateral stability then you are back to JF's method.

Airbedane, thanks. I thought that they had but have never had the privilege....!

[BEagle]

The effect of stiction in the aileron circuit can mask certain rigging errors....

When 'my' Bulldog (XX546) returned from its alleged servicing by the blacksmtihs masquerading as maintenance personnel at Abingdon, my press-on-itis boss passed it fit. I thought it was a piece of $hit with very unpleasant lateral stability characteristics, whereas previously it had responded very nicely. So I snagged it for 'unacceptable lateral stability characteristics due to excessive aileron stiction'. Pratt of a boss was cross that, as I'd put the ac u/s, he couldn't achieve his hours target; however, the student who'd tried to practise accurate IF steep turns in it agreed that it felt very odd indeed.

It turned out that some idiot had overtightened a part of the aileron system instead of torqueing it up correctly. Pay peanuts, get monkeys! When correctly adjusted, it flew as nicely as ever it used to!

[Skylark4]

BEagle,
Don't be too harsh on the 'engineers', Most are not pilots and do not appreciate the finer points of aircraft handling. I'm sure the controls would have been 'full and free' and deflections etc would have been according to the spec.. I'm also sure that a consultation with them would also have achieved a result, in fact, your post suggests that, when the problem was pointed out to them, the fault was found, presumably by the same engineers. We are a team and you were only one part of it. The attitude of your C.O. is a bit suspect though. If the hours were short, perhaps you should have been ready to fly when the aircraft were a bit more often.
At the current rates, you are lucky to get monkeys. The current rate, after removing shift pay etc. is less than £13,000 per annum, probably a bit less than you used to get as 'Flying Pay' and even that should now be called'payment for being able to fly an aircraft if I really had to'. I'll willingly swap my pay for your Pension.

Mike W

Edited to add:-
The 'Engineers' were, I guess, I wasn't there then, entirely ex RAF fitters and riggers so perhaps you should blame the RAF training they had. There are still one or two left who will remember you. Do you want me to look into it furthur?

Mike W

[Scion]

John, Lom and BAeagle,

Firstly thank you for your kindness in replying to my query and indeed you were quite correct.

Easing the stricture of the cable runs to the wings made a lot of differance , I carried out your suggestion of a stability test and the aeroplane is only marginally negativly stable. Thank you very much. By the way BA eagle have you had anything to do with Geoff Greens BA Eagle, operated by Mark Miller at all. When you come to Sydney you may like to try one with a retractable u/c and believe it or not fairly good brakes.

John and Lom also if coming to Sydney let me know!