That must have been it, my memory is fuzzy about the date, I was thinking later.

Since we are on the subject of TR's, I will tell the story of the mousetraps, which may be a repeat.

During initial Citation TR development, the stress group got in a snit about what would happen during TR transit if the pilot was pushing forward on the thrust levers at the same time the TR feedback mechanism was pulling them back.

The result was a deformable bracket which would prevent damage to the rest of the throttle cable system. This turned out to be problematic, so it was replaced by a spring loaded, one way over center mechanism informally called the mousetrap.

Well, what can go wrong will go wrong. There was a Citation that had a landing problem (don't remember exactly what, maybe a bounce), attempted to go around with the TR's in transit, popped the mousetraps and ended up in the trees.

This naturally got the FAA and NTSB attention. We unsuccessfully tried to develop an electrical mechanism which would lock the mousetrap with weight not on wheels. We ended up doing a test showing that the throttle mechanism would not be damaged (enough spring in the system) and went with removing the mousetraps.

Must have been this one. Tripped the load limiter and bye bye engine power. Load limiter can apparently only be reset on the ground.

https://aviation-safety.net/database/re ... 19890227-0

Citation 500/501 Operating Manual for example makes clear not to advance throttle until the TR unlock light is extinguished lest you really mess things up.

I was never a Citation guy, but I've always loved the airplanes. I grew up fascinated with the 501SP and the Learjet.

I did get to spend several years of my life flying various models of Lears.

Never did get an actual T/R deployment in flight, but I did have an unlock light that led to a precautionary shutdown IAW the QRH procedure, an emergency declared and a single engine landing.

Food for thought when talking about the efficacy of thrust reversers and the associated threats.

Some of us lower level peons questioned the benefits of thrust reversers for the Citation class in trade for cost, weight, maintenance, failure potential, etc., but management determined the market demanded them. That changed when the CJ series came around.

One more TR story.

The FAA was normally insistent that a FAA pilot be onboard for most certification flights, but decided it was not really necessary for TR inflight deployment tests and delegated it to the Cessna test pilot.

That's congruent with FAA flight test in the early sixties, when they insisted on a Lear 23 go-around with spoilers deployed - single engine. It resulted in the loss of the Prototype Lear 23.

All this talk about thrust reversers obscures what I'd really like to see on some of these crappy jets. (Read that 737-800's and 900's with their artificially high [Read that stupid] target speeds.)

A dragchute.

The young pilots I'm flying with think I'm kidding when I talk about the 'chute on the 20 and 20 series Learjets.

That's congruent with FAA flight test in the early sixties, when they insisted on a Lear 23 go-around with spoilers deployed - single engine. It resulted in the loss of the Prototype Lear 23.

All this talk about thrust reversers obscures what I'd really like to see on some of these crappy jets. (Read that 737-800's and 900's with their artificially high [Read that stupid] target speeds.)

A dragchute.

The young pilots I'm flying with think I'm kidding when I talk about the 'chute on the 20 and 20 series Learjets.

That doesn’t make sense. Mustang Vref speeds are typically between 85-90kts. It lands reasonably short. 1,000’-1500’ rollouts after touchdown are typical. Even with contaminated runways, the numbers are still good. Ice is the only no-go. TRs add weight, reduce thrust, shorten range, and don’t improve landing performance on a smaller airframe.

That doesn’t make sense. Mustang Vref speeds are typically between 85-90kts. It lands reasonably short. 1,000’-1500’ rollouts after touchdown are typical. Even with contaminated runways, the numbers are still good. Ice is the only no-go. TRs add weight, reduce thrust, shorten range, and don’t improve landing performance on a smaller airframe.

That's next level stupidity, disabling the UNLOCK lights just to turn them off. They exist precisely to warn you about the TRs being unlocked.

Surely this cannot be honestly used to claim TRs are bad.


The hydraulic system doesn't develop pressure until commanded by a system. With the TR breaker pulled, the TR system cannot command hydraulic pressure. That is why the TR stayed put until gear was retracting, that created hydraulic pressure which then deployed the TRs due to them being unlocked (that is, prepared to be deployed).

I religiously do TR tests before flight, and practice uncommanded TR deployment in training. I really like having them for short, wet, snowy, or icy runways.

Mike C.

TRs significantly improve landing and takeoff performance when the runway is other than dry. If your mission profile can assure dry and/or long runways, no need for TRs. Otherwise, they are very useful to improve dispatch reliability.

The penalties you list are quite small, in the 1-2% range. TRs save money on brake overhauls, so they are a net cost reducer.

My oldest brake stack is 10 years old, has ~900 landings on it, and has 70% life left. The typical 525 has done one or two brake overhauls in that time.

Mike C.

Been to all of them. For winter ops, 1/8" wet snow or 1" dry packed snow yield the longest landing distances (other than wet ice, which is a no-go). Even with those conditions, landing distances are still within 75% or less of runway length at any of them for a Mustang. TRs wouldn't make a significant difference.

My brakes have 720 landings with plenty left. Landing at 6500-7500 lbs has its benefits.

Out of curiosity, do they give you TR deployments right after takeoff? I am assuming in the sim. I don't know whether we ever tested that or determined the performance loss.