NTSB Wants Changes to Learjet 60 Thrust Levers

[Basil]

Have you had one or two tires blow out then had the TR's stow while trying to abort? or hit a dear on landing and have the TR's stow while trying to stop?

A couple of accidents have had this as a factor, I think it is a bad design of the controller and needs changing.

I don't see the FAA requiring the changes that the NTSB recommended. SB 60-78-7 was intended to cure the "squat switch was destroyed, thus reverting to air mode and stowing the deployed reversers" scenario by adding wheel speed as a substitute for the squat switches. The KCAE Lear-60 would have had this installed when delivered, but the wiring from the wheel speed generators was likely destroyed by the tire debris.

As I understand the system, for what happened to have occured, the first tire would have blown, the crew aborts, successfully deploys both T/R's beyond idle, then either squat switch would have had to have failed from debris (air mode) and debris also must have damaged the wheel speed generator wiring to make the T/R's stow. Both engines would have gone to idle (or more likely momentarily toward idle), the thrust lever T/R balk would have tried to engage to prevent rearward piggyback movement (but piggybacks already beyond the balk), then after the T/R's had fully stowed, the engines would faithfully deliver commanded thrust, likely around 90% N1. I believe that Antiskid may also have been lost with the squat switch/wheel speed gen loss, probably causing the other tires to fail as well.

We can "Monday Morning Quarterback" the crew's actions and Learjet/Bombardier engineering, but this accident started with an under-inflated tire. In my experience, tire inflation tends to be one of the most underlooked parts of the airplane on preflight. While the -60 may indeed have relatively high pressure/small volume tires, I don't know that the -60 has the lion's share of tire failures. To single the -60 out for a 96-hour tire pressure check is to make it a scapegoat.

Everyone on every aircraft should be checking tire pressures.

 

[LJ45]

I agree on checking the tires, we carry a gauge. The problem is Part 135, the pilots can't check them. That can be a big problem on RON's in remote places.

Maybe the wires and switches need more protecting. If you ever look at the 45 gear the switches are protected by design comparted to the 60.

 

[Basil]

Crane Aerospace is developing a wireless tire pressure and temperature sensor for the -60. A wand would be held close to the valve stem and the pressure would be transmitted via RF to the wand. Hopefully that would be an easy approval for 135 pilots to check.

http://www.craneae.com/Products/Sensing/SmartStem.aspx

Until recently, I was guilty of the "they look okay" preflight. Not anymore.

 

[SpeedRestricted]

Crane Aerospace is developing a wireless tire pressure and temperature sensor for the -60. A wand would be held close to the valve stem and the pressure would be transmitted via RF to the wand. Hopefully that would be an easy approval for 135 pilots to check.

http://www.craneae.com/Products/Sensing/SmartStem.aspx

Ah thanks, I have been looking for that. Do you have any idea of the development/approval time frame for the 60?

 

[Fly91]

Crane Aerospace is developing a wireless tire pressure and temperature sensor for the -60. A wand would be held close to the valve stem and the pressure would be transmitted via RF to the wand. Hopefully that would be an easy approval for 135 pilots to check.

http://www.craneae.com/Products/Sensing/SmartStem.aspx

Until recently, I was guilty of the "they look okay" preflight. Not anymore.

Great, lets add another expensive piece of equipment to an airplane that can give a bad reading and/or fail so another accident can happen on a Lear 60. The FAA needs to make it a mandatory physical check by the pilot along with the 96hr rule.


.

 

[SpeedRestricted]

Great, lets add another expensive piece of equipment to an airplane that can give a bad reading and/or fail so another accident can happen on a Lear 60. The FAA needs to make it a mandatory physical check by the pilot along with the 96hr rule.

Nobody is saying you have to buy it, but it would certainly make it easier. If it fails then use a regular gauge, I'm not totally educated on the technology being used, but I know it is already in use on other aircraft, including the 777. Maybe a 777 mechanic or pilot can chime in on any problems with bad readings, but last time I checked all equipment is subject to failure, inaccurate readings, and especially operator error, including conventional pressure gauges.

 

[Basil]

Great, lets add another expensive piece of equipment to an airplane that can give a bad reading and/or fail so another accident can happen on a Lear 60. The FAA needs to make it a mandatory physical check by the pilot along with the 96hr rule.


.

I think it's a great idea. You can bet it won't be cheap, but as long as it's reliable, it will prevent the frequent small pressure losses caused by checking the pressures with a conventional gauge.

 

[Basil]

Ah thanks, I have been looking for that. Do you have any idea of the development/approval time frame for the 60?

I heard the goal was by the end of 2009.

 

[LJ45]

On Bombardier's CIC website, it states that 135 operators can get approval from their POI to have the pilots check the tire pressure under part 135. If the tire pressure is low, it must be serviced by A&P not by a lowly unskilled Pilot. ok, the lowly part I made up...ha

 

[Fly91]

Nobody is saying you have to buy it, but it would certainly make it easier. If it fails then use a regular gauge, I'm not totally educated on the technology being used, but I know it is already in use on other aircraft, including the 777. Maybe a 777 mechanic or pilot can chime in on any problems with bad readings, but last time I checked all equipment is subject to failure, inaccurate readings, and especially operator error, including conventional pressure gauges.

Thats what I mean, why add another piece of equipment that can give you a bad reading and the crew will trust that its correct, and have another accident because of it? Not smart. Pilots will get used to just using that and they'll never bend don to really check the tire pressure with a guage. But thats aviation.................


.