727 Nose Wheel Brakes

[SOPS]

In an anarak moment a few weeks ago, I bought a Flight Engineers Training Manual for the 727 that I found in a second hand shop.

It has being very interesting reading so far. I am up to landing gear and it is now talking about the anti skid controllers for the NOSE WHEEL brakes.

I never knew that the 727 (or any aircraft for that matter) had nose wheel brakes.

Can you very knowlegable people please tell me more?

[Flight Detent]

Hi SOPS,

Many years ago I flew the 727-200 series airplanes for around 3,000 hours.

I seem to recall that the nose wheel brakes only operated when maximum braking was employed.
That is, they were very rarely utilized, to the extent that cannot recall them ever intentionally being used at all!

Great airplane, started in 1988 with the B727-238-15, and ended up operating the B727-269-17R, before moving on to the B747-200 series in 1994.

Great memories...

Cheers...FD...:)

[gearguy]

Hello,

Based on the repair manual for the NLG, brakes on the 727 NLG were an option - the NLG can be built with them or without them.

Brakes on NLGs are rare: fighter aircraft for unprepare surfaces/icy surfaces being one of the few places you tend to see them (SAAB, MiG).

NLG brakes can be normal brakes used to shorten stopping distances (either to squeeze the aircraft into a shorter runway than normal - maybe the 727 case) or small brakes to stop the wheel rotation prior to retraction (this is usually done by straps in the NLG bay - a lighter and cheaper and more reliable option).

[Good memories]

Hi SOPS,

By my best knowledge the Convair CV-990 Coronado was one of the few commercial planes equipped with a nose wheel braking system.. It was the contender of the B 707 and DC 8 in the 60'ties. Swissair was one of the few companies who bought them new. I remember the approach speeds were rather high .


Good Flying!


John

[hetfield]

Yeah NLG were an option. In our fleet we used to have more than ten aircraft equipped with NLG but I never heared of a replacement because they simply were not used. It's long ago but AFAIK the pedals had to be deployed to their maximum to activate them. (was there also a speed limit for them, don't remember?) There is very good reason for that. Everybody who has ever ridden a motorbike knows the forces up front during braking. So on the 727 nose gear strut the torque had to be limited not to overstress the strut. An option to get some better numbers on the performance charts like the option of rockets for engine failure on high elevation airports like La Paz.

[PantLoad]

Yep, I flew the three-holer, as well....even sitting sideways.

The nose gear brakes, if equipped, were typically removed by most operators. Less weight, no maintenance, no need.

The 727 had great stopping capability. Never flew one with the nose wheel brakes....others have told me the thing really stops on a dime
when using the nose wheel brakes.

Fly safe,

PantLoad

[SOPS]

You guys are the best:ok:

[By George]

Ansett had the 727-200LR (long range) with nose wheel brakes. The penalty for them being u/s was 3000kg to the T/Off weight, so they must have had some effect on the accelerate/stop performance. Why remove them? Brakes are like engines, you can never have too many.

[muduckace]

Worked on a private -100 with nose gear brakes active in the late 90's. They kept them for short field performance at SKI resorts and small island strips. Belly's were all tanker fuel and they had in-flight oilers as the aircraft could fly longer than the oil supply would last in those old JT8's.

[stilton]

In flight Oilers, how did they work ?

[Spooky 2]

Singapore had NWB on their 727-212 Adv. EAL also had NWB along on some of their 727-225Adv. aircraft. I believe both of these aircraft also had an AutoBrake function along with Auto Speedbrakes, ala B757/767.

[muduckace]

Been allmost 15 years but I remember engineer panel switches and a oil resevoir in the aft air stair area.

You perked my curiosity and I found a Trump -100 with oilers and a picture of the switches, far aft in the center of the panel. Worth a look anyways, this is one fine private jet.


Boeing 727-100 S/N: 20046 For Sale (http://www.avprojets.com/view_aircraft/162/Boeing_727-100_SN_20046.html)

[Romeo E.T.]

if my memory serves me correct from my 3000hrs on the B727-200, the nose gear brakes came efective after 70% brake pedal deflection, were hardly ever used, but remained installed due to the accel-stop performance advantages this gaves us.

[Runaround Valve]

Flight detent in Post#2 states that he operated on Boeing 727-238-15.
Now, 38 is a Boeing customer number for Qantas and Qantas never bought or operated Boeing 727 aircraft.

[MarkerInbound]

I've run across a couple 727 that still have the nose brakes in the last couple years. The rationale given was that the plane would have needed ballast anyway so why not carry something that might be useful some day v. bags of lead shot.

The oilers are popular with the VIP planes. Some of those planes are running around with the bellys stuffed with fuel, 80,000+ pounds at takeoff.

[18-Wheeler]

Flight detent in Post#2 states that he operated on Boeing 727-238-15.
Now, 38 is a Boeing customer number for Qantas and Qantas never bought or operated Boeing 727 aircraft.

I suspect he typed that by accident, he meant 727-276.

[JammedStab]

if my memory serves me correct from my 3000hrs on the B727-200, the nose gear brakes came efective after 70% brake pedal deflection, were hardly ever used, but remained installed due to the accel-stop performance advantages this gaves us.

I believe that for nosewheel braking, 50% deflection of both brake pedals will activate nosewheel steering OR 75% deflection of any one brake pedal. If nosewheel brakes are installed, wheelwell fire sensing is installed in the nosegear bay. If I remember correctly, I believe that it is a single anti-skid unit for both nosewheels. Nosewheel braking is 'A' system operated unlike 'B' system main brakes.

There is a separate switch in the cockpit to deactivate the nosewheel brakes, however, nosewheel braking is also deactivated when the main gear anti-skid switch is turned off according to my manual, although nosewheel braking will still be applied upon gear retraction.

Brake wear indicators are checked with the park brake on. With the park brake set, the nosewheel brakes are not applied. Therefore to check the nosewheel brake wear indicators, you would release the park brake, have the ground interconnect open and at least one of the 'B' pumps on(electrically powered) with someone applying the brake pedals in the cockpit while you check the wear indicators on the nosewheel. Having the 'B' pump on with the ground interconnect open operates the 'A' hydraulic system.

The nosegear does have a single lockout debooster valve like each main gear brake has in order to deboost hydraulic pressure, provide leak protection and fluid quantity adjustment on the low pressure side of the valve as the brakes wear. Below that valve on the nosegear is the replenishing switch used to operate a solenoid to pressurize the nosebrakes for ground inspection and servicing(with 'A' system hydraulics available).

At least that is what my old notes say.

[hetfield]

The nosegear does have a single lockout debooster valve like each main gear brake has in order to deboost hydraulic pressure, provide leak protection and fluid quantity adjustment on the low pressure side of the valve as the brakes wear. Below that valve on the nosegear is the replenishing switch used to operate a solenoid to pressurize the nosebrakes for ground inspection and sevicing(with 'A' system hydraulics available).

Exactly.

Concerning activation of NLG. As a former FE I had to check the NLG with the replenishing switch and A pressurized in the morning. So someone in the cockpit had to push the pedals. ALL stated afterwards that they had to push it almost to the mechanical limit to activate the brakes.

[Dodo56]

In 15 years of running workshops doing wheels among other things I only ever saw one 727 NW brake, and I reckon from the state of it that had last been serviced 15 years previously!

The wheels themselves had drive keys as you might expect, and these keys aren't cheap. Many workshops never bother to look at them so when you overhaul the wheels and measure/NDT the keys per the CMM it's a fair bet that you'll reject some of the keys for wear or corrosion. When we did this not one customer wanted the keys replaced, they all opted to convert the wheel to an alternative P/N (basically just remove the keys).

[Flight Detent]

Thanks "18-Wheeler"...

My mistake..you are quite right!

They were Australian Airlines airplanes.

Cheers...FD

[galaxy flyer]

Spooky 2

EAL had NWB on the earlier planes, but I don't think -200A had NWB. I got there in 84 and all the NWBs had been removed from the 125-strong fleet.

GF

[Dan Winterland]

I think the Convair jet airliners also had NWB. The first jet with it must have been the Me262. Mainwheel brakes activated by pedals and the nose by a squeezy grip (like a bike) on the control column.

[Spooky 2]

Galaxy Flyer, reread my post as I think that is what I said, or least meant. :}

The former -225ADV aircraft had the brakes. These wound up at Delta Airlines.

[galaxy flyer]

Spooky 2

Sorry 'bout that--I didn't think the -225ADV ever had them installed, only the -100 and -200. Learned something.

GF

[virginpaul]

I worked for Iberia in the very late '80's and they had the 727-200 with some equipment for the Nose Gear Brake system installed (boosters and some pipework in place in the NWW) but not used (no brakes fitted). The nose wheels still had the drive lugs for the brake rotors at that time.
Paul

[EAL shuttle]

Yeah NLG were an option. In our fleet we used to have more than ten aircraft equipped with NLG but I never heared of a replacement because they simply were not used. It's long ago but AFAIK the pedals had to be deployed to their maximum to activate them. (was there also a speed limit for them, don't remember?) There is very good reason for that. Everybody who has ever ridden a motorbike knows the forces up front during braking. So on the 727 nose gear strut the torque had to be limited not to overstress the strut. An option to get some better numbers on the performance charts like the option of rockets for engine failure on high elevation airports like La Paz.
This is a very good observation. I was blessed with the pleasure of flying the B727 for 7k hrs. NWB were expensive to maintain. Therefore, some companies de activated them on airplanes so equipped. I recall flying to Wilkes Berry Scranton in the winter, NWB were mandatory for dispatch.
Jose

[CV880]

Re post #4, yes the Convair 880/990 had nose wheel brakes. To the best of my recollection they only operated when the brake pedals were fully depressed (desperation mode) and were either full on (relying on the antiskid to prevent lock up) or off. Nosewheel steering inputs beyond a certain point would also release the nw brakes if applied. The nosewheels were on a common axle with a single antiskid transducer and antiskid valve. I think they might have looked after the spin down braking on retraction but it was a very long time ago. I believe there was an incident, before my time on 880's, where one had full nosewheel braking applied on touchdown due to a malfunction and came to a rapid stop with square nose wheels and damage to the bottom end of the nose leg. I cannot recall ever replacing nosewheel brakes due to wear.

[Obama57]

I think EAL had 3 -17’s used for South America - La Paz that had oversized MLG wheels, nose brakes, and “black power” ( higher EPR with an engine failure on takeoff.) I started in ‘79 and the nose brakes were all deactivated by then.

[CVividasku]

I don't recall if anyone said it, but nosewheel brakes should be helpful at every flight to reduce wheel vibration when gear is retracted, as is done on the main gear wheels.
I wish we had that type of brakes on the A320. They would only require a very small brake system, and would not impact navigability in case of failure/absence.

[tdracer]

I don't recall if anyone said it, but nosewheel brakes should be helpful at every flight to reduce wheel vibration when gear is retracted, as is done on the main gear wheels.
I wish we had that type of brakes on the A320. They would only require a very small brake system, and would not impact navigability in case of failure/absence.
The problem with making a nosewheel braking system basic is then it has to be part of the MEL. While you can dispatch with the system inop via the MEL - there must be a time limit associated with the MEL dispatch - so you'll eventually have to spend the money to fix it. So the operators would need to pay the cost of adding the feature, then spend more money keeping it working to avoid having aircraft grounded.
Operators don't like that - especially when a cheap, simple snubber in the nose gear wheel well gets the job done (if perhaps not very gracefully).