UH-60A Question

[Ian_J]

For anyone who knows... it's driving me crazy:

Why does every EP about a CHIP in any engine or transmission module involve shutting down an engine or simply landing as soon as possible except for an input module chip which has you retard the affected PCL to idle (as opposed to simply an emer eng shutdown) and then landing as soon as possible. Why isn't it like an accessory module chip? What is the purpose of putting the PCL to idle?

 

[jtrain609]

I haven't flown the UH-60 in a while, but my guess is that you don't want to run the thing oversquare, and they'd also like you to then put it down quick, but while you're in the flare, cancel your flight plan as you're autorotating the flaps.

 

[Ian_J]

Thanks John, that's a big help. I already do all that stuff you mentioned but it just occurred to me I never extend the gear at the marker and I haven't calculated a start-stop distance yet or practiced a V2+23 cut yet. Lots to learn...

 

[jtrain609]

Thanks John, that's a big help. I already do all that stuff you mentioned but it just occurred to me I never extend the gear at the marker and I haven't calculated a start-stop distance yet or practiced a V2+23 cut yet. Lots to learn...

My CFI is still current, let me know if you want to schedule some dual and we can get you squared away.

 

[Ian_J]

My CFI is still current, let me know if you want to schedule some dual and we can get you squared away.

My CFI is current too - heard you were having problems with your auto-rotations at XJT... we could just trade services.

 

[jtrain609]

My CFI is current too - heard you were having problems with your auto-rotations at XJT... we could just trade services.

Sounds like a plan. Where are you in the world, these days? Maybe I'll try to get an overnight there and we could give each other BFR's at the bar.

 

[MikeD]

For anyone who knows... it's driving me crazy:

Why does every EP about a CHIP in any engine or transmission module involve shutting down an engine or simply landing as soon as possible except for an input module chip which has you retard the affected PCL to idle (as opposed to simply an emer eng shutdown) and then landing as soon as possible. Why isn't it like an accessory module chip? What is the purpose of putting the PCL to idle?

In the HH-60G, essentially the USAF A-model, the different procedures are as follows:

CHIP (#1 ENG, #2 ENG): 1. Throttle- Retard to reduce TRQ. 2. Land as soon as practical.

CHIP INPUT MDL (LH or RH): 1. Throttle (Affected Engine)- IDLE; 2. Land as soon as Practical. If MAIN XMSN OIL TEMP caution light ON, XMSN TEMP exceeds normal operating limits and/or noises or vibrations occur: 3. Land as soon as Possible.

They're all Land as soon as Practical, with Possible only being for additional factors mentioned above.

I imagine its possibly because the inpit module contains the freewheel unit, and you don't want anything affecting the freewheel unit from disengaging the engine from the transmission, something that chips rolling around in there may do. So you take care of the freewheeling early by retarding the PCL to idle for the affected engine.

 

[Ian_J]

Sounds like a plan. Where are you in the world, these days? Maybe I'll try to get an overnight there and we could give each other BFR's at the bar.

PM-ing. Though I doubt your sincerity because I know you've been drinking.

In the HH-60G, essentially the USAF A-model, the different procedures are as follows:

CHIP (#1 ENG, #2 ENG): 1. Throttle- Retard to reduce TRQ. 2. Land as soon as practical.

CHIP INPUT MDL (LH or RH): 1. Throttle (Affected Engine)- IDLE; 2. Land as soon as Practical. If MAIN XMSN OIL TEMP caution light ON, XMSN TEMP exceeds normal operating limits and/or noises or vibrations occur: 3. Land as soon as Possible.

They're all Land as soon as Practical, with Possible only being for additional factors mentioned above.

I imagine its possibly because the inpit module contains the freewheel unit, and you don't want anything affecting the freewheel unit from disengaging the engine from the transmission, something that chips rolling around in there may do. So you take care of the freewheeling early by retarding the PCL to idle for the affected engine.

Interesting - on the Army model for an engine chip the procedure is the same as far as retarding the PCL, but they add if oil pressure is low or temp is high to do an emergency engine shutdown. And our Chip Input module is PCL Idle, then Land as Soon as Possible, not practical.

And yeah, I agree the freewheeling unit needs to be protected, but why idle instead of just shutting the engine down? Maybe it's a "just in case" thing, like maybe if you need the engine power in a critical situation you could advance the PCL - something you couldn't do if you shut it down?

 

[MikeD]

And yeah, I agree the freewheeling unit needs to be protected, but why idle instead of just shutting the engine down? Maybe it's a "just in case" thing, like maybe if you need the engine power in a critical situation you could advance the PCL - something you couldn't do if you shut it down?

Agree. If you freewheel it, then need it later, you can simply advance the PCL back to FLY and its there for you, albeit with an INPUT MDL CHIP still there. But, if the other engine is a complete failure for whatever reason, then the former situation is the lesser of two evils.

 

[Ian_J]

Makes sense to me. The Blackhawk is a strange animal. In a Chinook any left/right side transmission problems were usually solved by shutting down an engine. But with the blackhawk, you get a mix of things. For example - an accessory module chip is a land as soon as possible. That's it. I don't get why you wouldn't just shut down that engine and drive on.

 

[MikeD]

Makes sense to me. The Blackhawk is a strange animal. In a Chinook any left/right side transmission problems were usually solved by shutting down an engine. But with the blackhawk, you get a mix of things. For example - an accessory module chip is a land as soon as possible. That's it. I don't get why you wouldn't just shut down that engine and drive on.

Possibly because Transmission fluid is what cools the #1 and #2 GENs via their respective Accessory modules. You get a chip blocking one of those and end up trashing out a GEN is maybe why. Insofar as shutting down the engine and driving on, that same Transmission fluid is flowing back through the transmission, and you'll likely start getting more chip lights in bad places. Plus, the -60 is so power limited anyway at the weights we fly them at, that single engine for non-combat ops is likely not worthy. Combat ops-wise, you can likely just dump fuel and press to a safe area.

For anyone who knows... it's driving me crazy:

I find it hilarious that you put this detailed question out to the masses of SJSers here in General Topics

 

[Ian_J]

Possibly because Transmission fluid is what cools the #1 and #2 GENs via their respective Accessory modules.

I figured this, but thought "big deal," much like the -47 losing a Gen and a Hyd Pump is no big deal. We have lots of them.

Insofar as shutting down the engine and driving on, that same Transmission fluid is flowing back through the transmission, and you'll likely start getting more chip lights in bad places.

That's right... the -47 has two independent transmission fluid systems and the -60 doesn't.

Plus, the -60 is so power limited anyway at the weights we fly them at, that single engine for non-combat ops is likely not worthy.

Man, I miss the -47.

Seriously though - thanks for talking this through with me, Mike. Just BS-ing back and forth about it made things a lot more clear in my head.

 

[Firebird2XC]

For anyone who knows... it's driving me crazy:

Why does every EP about a CHIP in any engine or transmission module involve shutting down an engine or simply landing as soon as possible except for an input module chip which has you retard the affected PCL to idle (as opposed to simply an emer eng shutdown) and then landing as soon as possible. Why isn't it like an accessory module chip? What is the purpose of putting the PCL to idle?

I don't know for certain, but I have a few theories:

1) The input module is directly connected to the main transmission module and share oil flow. Accessory modules share the same oil supply, but there are filter screens in the supply and return tubes, so debris from a gear throwing chips will be contained. The main transmission has a chip detector with a 'fuzz burner', so anything big enough to cause a chip there is likely cause for immediate concern. The input module chip detectors IIRC directly are simply catching particles in the total oil flow of the main transmission supply. The source of the chip may be less determinant, so a reduction in PCL setting to Idle to maintain engine power to the accessory module (and associated hydraulic pump and generator) would be useful.

2) The Input module seems like it would have some the highest opposing loads in terms of shearing forces, so reducing engine torque would likely significantly reduce the forces producing chips in that particular module.

3) It's the 'Hawk. Chips and special oil samples in the A model were just a way of life after a while. The planetary gears in the main transmission module starting having problems in the late 90's or so and required a lot of extra care as a result. I've drained and flushed the main transmission due to special consideration more times than I care to remember. It's possible that because of the previously mentioned filter screens/fuzz burner items that the Input mod lacks that somebody in the Army decided that this procedure was just safer that way.

 

[dustoff17]

I don't know for certain, but I have a few theories:

1) The input module is directly connected to the main transmission module and share oil flow. Accessory modules share the same oil supply, but there are filter screens in the supply and return tubes, so debris from a gear throwing chips will be contained. The main transmission has a chip detector with a 'fuzz burner', so anything big enough to cause a chip there is likely cause for immediate concern. The input module chip detectors IIRC directly are simply catching particles in the total oil flow of the main transmission supply.......

SHOULD be contained. As said here before, the transmission shares oil throughout the entire system. Example: The right module is shedding off metal pieces but the left detector picks it up through the continuous flow of oil. This is a very likely scenario with this system. Bringing the right engine to idle keeps the oil flowing via oil pumps/accessory gear box and it leaves that power there if you need it. If you shut down the right engine and then the left input module shears (or comes apart), you would be without either engine.

.........3) It's the 'Hawk. Chips and special oil samples in the A model were just a way of life after a while........

Many of the continous oil samples were really to keep the Oil Analysis Lab workers busy. No kidding!

 

[Firebird2XC]

SHOULD be contained. As said here before, the transmission shares oil throughout the entire system. Example: The right module is shedding off metal pieces but the left detector picks it up through the continuous flow of oil. This is a very likely scenario with this system. Bringing the right engine to idle keeps the oil flowing via oil pumps/accessory gear box and it leaves that power there if you need it. If you shut down the right engine and then the left input module shears (or comes apart), you would be without either engine.

Ahhh.. That makes total sense. In this case, then, bringing the PCL to idle on the chip lighted module keeps a false 'cross-indication' from leading you to shut down the engine on the healthy side of the transmission system.

Many of the continous oil samples were really to keep the Oil Analysis Lab workers busy. No kidding!

This piece of information really makes me wish I'd succumbed to my secret wish to slip the AOAP kids a cleverly disguised urine sample instead of oil. Knowing that my workload and one of my least enjoyed tasks were bumped up as busy work just makes me roll my eyes.

 

[dustoff17]

This piece of information really makes me wish I'd succumbed to my secret wish to slip the AOAP kids a cleverly disguised urine sample instead of oil. Knowing that my workload and one of my least enjoyed tasks were bumped up as busy work just makes me roll my eyes.

:rotfl: