Maintenance Tip: Brakes – OEM versus STC

Maintenance Tip: Brakes – OEM versus STC

All King Airs come out of the factory with BFGoodrich brakes, and most come with a multi-disc brake assembly. The only exceptions were the F90s and the 100s (straight A and B models) with standard gear, which came with a single-disc brake assembly by BFGoodrich (BFG). The multi-disc brakes by BFG have excellent stopping capability, but they’re very expensive to maintain.

Internal Multi-Disc

The multi-disc brake assembly is considered an internal disc setup. The discs fit together; the wheel, with special cut-outs to accommodate the disc assembly, slides around the discs. Relining or overhauling these items is very labor-intensive. The usual practice is to purchase an exchange brake unit. Your core unit is then returned for evaluation and credit (hopefully) against the core value. But as we have seen over and over, in recent years, most cores (everything from brakes to fuel probes) generate a core charge billback. The rotable pool has aged, and some of the components needed for overhaul are so scarce they must be replaced with new. As the cost to overhaul a unit has increased, the core charge values have skyrocketed.

These days you can buy an exchange widget in overhaul condition with a core value nearly equal to a brand-new widget. Then, upon evaluation, if your core widget is deemed BER (Beyond Economical Repair), you end up paying the exchange price plus the nearly new price for a used widget. Even if your core isn’t completely condemned, you can bet on a billback, and a hefty one at that. Core charge billbacks, once the exception, are now the norm. But I digress …

External Single-Disc

When it comes to the BFG multi-disc brake assembly, their exchange units have always been exorbitantly expensive. In response, Cleveland developed a brake conversion kit that gets rid of the internal multi-disc setup in favor of an external single-disc setup with two calipers per disc. While the stopping power of these brakes is not quite as good as the multi-disc assembly, these Cleveland conversion brakes are still very good. It only takes a little bit to get used to them.

A diagram from the King Air 90 manual (left) shows the internal, multi-disc BF Goodrich brakes that come on most King Airs out of the factory. The King Air 90 wheel diagram (right) portrays how the brake is sandwiched between the two wheel halves.

Conversion Kits for Standard Gear

The upfront cost of converting to Cleveland brakes is a bit steep because you must replace the wheels. The kit for the STC includes new wheels plus all the other brake components – calipers and pucks, discs and linings, seals and hardware.

The payoff for the conversion comes later when it’s time to change your brakes, as they are easily disassembled. The worn parts are replaced, the brake is reassembled, the fluid is serviced, the lines are bled, and you are good to go. The cost of replacement components is more now than back in the day, but even so, the savings are huge and well worth it in my opinion.

Single Truck versus Double Truck

All the 90 series King Airs, except the F90, have a single truck gear, and this poses a little extra hitch when completing the Cleveland conversion. The wheel wells require a minor modification. This should only take a few additional hours of labor.

King Air models with double truck gear (the F90, 100, A100, B100, 200, B200, B200GT) can get a Cleveland conversion, even with if they already have the soft touch tire STC. No additional sheet metal work is required because the wheel well requires no modification. The conversion is almost as simple as changing the tires. But I’m still talking standard gear here. (High float gear and 300s/350s, hold short, you’re next.)

Another advantage to the external single-disc is the comparative ease in fixing a leaky O-ring on a puck. There is much less labor involved. As far as I’m concerned, the significant savings in maintenance costs with Cleveland brakes on standard gear far outweighs the slight difference in braking performance.

High Float Gear

King Airs with high float gear also come from the factory with BFG multi-disc brakes. You may know from experience that the lining is very thin. They can wear out very quickly, depending on how you use your brakes. I’ve seen pilots wear them out in less than 200 hours because of heavy braking on landing and/or riding the brakes on taxi. I think everyone with high float gear knows this already, so I’m just preaching to the choir.

Unfortunately, there isn’t a great alternative to the OEM brakes on high-float gear. Yes, Cleveland makes a conversion kit, but it’s not much different from the OEM brakes installed by the factory. The Cleveland kit for high float gear has internal multi-disc setups just like the BFG brakes, but the cut-outs in the wheels are slightly different, so the kit includes new wheels. It’s a lot of money to spend, and for what?

For those of you with high float gear, I recommend you research your logbooks and POH to verify with certainty whether your brakes are OEM or STC’d. You cannot tell the difference until you take them apart. I learned this the hard way many years ago when I was exchanging the brakes on a King Air with high float gear. For some reason, they just didn’t look like BFG to me, so I ordered Cleveland exchange parts. When I tried to install them, the BFG wheels would not slip over the Cleveland brake assemblies. That was the last time I made that mistake!

A Cleveland-manufactured brake on a King Air 90 shows the external single disc setup.

The 300 Series

Finally, for you 300 and 350 drivers – I got nothin’! All 300 series King Airs have standard gear with the same OEM brake assembly as the other double truck King Airs; but strangely, Cleveland has no STC’d conversion kit for these models. I’m guessing that the extra gross weight is a factor and that the external single-disc setup cannot meet the stopping distance requirement in the POH.

My only suggestion is to take care of your brakes and get the best wear out of them to extend the time between exchanges.

Burn Them In

Lastly, don’t forget that a new set of brakes, whether OEM or Cleveland, must be properly burned in before putting the aircraft back in service. Burning in new brakes ensures they have the proper stopping capacity, reduces the possibility of noise or chatter, and makes them wear better. This is a must-do. If your brakes were changed, or if you got new linings installed on your Cleveland brakes, make sure the shop did this.

I once had a customer with a C90 and a 200 on a 135 certificate. He arrived to pick up the 90 after service and I hadn’t yet burned in his new brakes. He offered to have his A&P do it, so I assumed he knew what I meant. Well … we all know what they say about the word “assume” – it makes a “you know what” out of “U” and “ME.” It turns out that his version of burning in new brakes was to burn them off! He taxied back in with smoke billowing behind him. His brand-new linings were burned completely away and he got down into the discs. The O-rings on the pucks were melted. I had to order and install new linings and new discs, plus rebuild all the calipers. Good thing they were Clevelands!

When you get new brakes, your best bet is to have your mechanic burn them in. Second best is to take him or her with you on the ground run if you have to do it.

In closing I’ll say this: Be nice to your brakes and let’s hope they don’t break the bank.

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1 Comment

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    wilfredbenitez March 3, 2020 at 7:17 pm

    Very nice write-up. I absolutely appreciate this site. Thanks!

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