Landing gear wheel brakes

[greybeard]

When were wheel brakes introduced in aviation? How were they made and how did they work? I have fragmentary data on the subject: an old print of the P-39 Airacobra where it talks about "Hydraulic Multi-Disc Brakes", a detail of the undercarriage of the Bf 109 showing a drum brake, I saw the brake of an F -15 with just one disc and five calipers! I would like to know a brief history of this device in its aeronautical use, with hints on the reasons for the various choices. Thanks anyway to anyone who knows something about it and wants to share it.
Sorry if my questions range from before and after the Second World War: I'm focused on it, but I would also like to understand how it got there and what legacy it left.

 

[Engineman]

One disc and five calipers! What you see on the inside face of many modern disc units is indeed the multi brake caliper face but, there are actually many disc rotors and friction stators built-up into a complete brake pack that fills the entire inside space of the wheel.
A good subject for further discussion!

Eng

 

[Engineman]

Some further thoughts about brakes.
In early days, the tailskid was just that-a wood skid, often with a steel shoe. That arrangement was simple but provided a bit of retardation with the tail on the ground and also some stability. However, even small aircraft required holding down for engine run-ups and the first "brakes" were people hanging-on to the tail or, a tie-down rope to a fixed post etc.
More convenient wheelbrakes became required as aircraft got heavier and more powerful. Without research, I would guess that aircraft wheelbrakes were developed after WW1 and some perhaps earlier than that. Automotive style manual drum brakes may well have led the way. Early brakes would have assisted handling of the aircraft and helped stop heavier and faster aircraft. The increasing speed, weight and power of aircraft demanded more powerful brakes. The energy required to be absorbed in stopping an aircraft on the ground increases directly proportional to the Mass, but also to the speed squared, so a doubled speed requires four times the braking power.
Drum brakes were very common until after WW2. Although the drums got larger, the force required to operate them demanded mechanical assistance, and compressed air or hydraulics became common. However, the drum brake is often limited in its ability to develop sufficient braking power and fading or overheating brakes were a common problem.
Disc brakes were developed to offer greater braking capacity, to deal with faster and heavier aircraft. The disc / caliper(s) arrangement can offer advantages in brake performance and cooling ability, with multiple discs and calipers, the performance can be outstanding. Additionally, hydraulic disc brakes can be supremely reliable and offer high service life.
To control the braking power of disc brakes, anti-skid systems were developed. Early mechanical anti-lock systems, like Dunlop Maxaret, used a small spinning wheel running on the inside of the aircraft wheel, that would stop spinning if the wheel locked. The small spinning wheel incorporated an inertia bobweight that operated a relief valve so that if the spinning stopped, the inertia bobweight operated the relief valve and released the brakes, until the wheel spun-up again.
Anti-skid systems developed further and electro-hydraulic versions used different wheel sensors. Eventually, digital systems with wheel sensors and complex electro-hydraulic operation were developed. Auto-Brake also became part of the picture and added extra safety to the whole ability of modern aircraft brakes.

Eng

 

[greybeard]

Thanks for your reply. Fascinating matter; although propelling an aircraft is undoubtedly more exciting, I thing to stop it is also important.

 

[Engineman]

Well,
Jet airliners particularly, have relied on modern brakes for their Certified safe performance. Stopping from a rejected Take-off, or from a max overweight landing and operating short sectors with short landings and short turnrounds rely almost entirely on brake performance. Runways are not always as long as optimal and reduced power take-offs (to reduce engine wear and tear) can increase the demands on brake systems.
There are some interesting videos of brake testing, worth a trawl on the net.

Eng

 

[cvairwerks]

Don't forget that Goodyear had a multicaliper, single disc brake system, The wheel was keyed to take a single floating disc and one or more calipers were mounted to the landing gear leg. The C-45/Beech 18's were one of the bigger users of this style brake.

 

[Engineman]

Don't forget that Goodyear had a multicaliper, single disc brake system, The wheel was keyed to take a single floating disc and one or more calipers were mounted to the landing gear leg. The C-45/Beech 18's were one of the bigger users of this style brake.

Yes, Goodyear do look to have been early on the scene with disc brakes. Looks as though the aviation side was ahead of automotive. Certainly, I see the P-51 with multiplate discs from the start.

Eng