Transmission chip detector scenario

[GeorgeMandes]

Last week, we made a 110 nm flight in a 75 hour TT Bell 407, of which 50 miles was over cold water across Cook Inlet in Alaska, with the balance across mountains. On descent, we got a transmission chip light, at 500 AGL on descent to our destination.

If we had gotten that same light, 25 miles from the closest shore, it would have been a different scenario then on final descent. Three questions:

1) what secondary indications of a real transmission problem would be expected -- for example, transmission temp and pressure, and noise?

2) at what altitude and airspeed would you fly in case the situation deteriorated?

3) under what scenario would you pop the floats and put it in the water?

Thanks.

PS: It turned out to be a bit of fuzz so small we couldn't ever see it, but that went away after blowing off the lower transmission chip detector probe with an air compressor.

[WASALOADIE]

Your reference cards, operating procedures or whatever you use should dictate the urgency to land.

As for secondary indications, you could get any of the three or multiples of them. Certainly the minimum would be to monitor T's & P's and if there is a rise in Temp or loss of pressure, consider the options of putting the a/c down before you're forced into the situation.

What are the sea temperatures at the time? what are your survival chances if you make a ditching. Can you always rely on a chip warning to be just a little bit of fuzz? Its a judgement call. Reducing height to a suitable height to be able to react and get the a/c safely down (not too low to give you no time to react), not to high to prolong the descent.

Thats where you earn your captaincy!

[Helinut]

Add to what Loadie says:

What was the sea state relative to the probable capability of the aircraft on floats to stay upright? If it was likely that a precautionary landing would lead to a capsize due to sea state, it changes the probable outcome of a precautionary landing on water.

Dynamic Risk Assessment of the outcome of the 2 alternatives:

Continue Flight; or
Precautionary Landing on water

[SASless]

Assuming you had floats.....and Cook Inlet was laying down....ditching is not too bad a risk. Going into Cook Inlet without survival suits even in the middle of the Summer is not a good Idea. The Coast Guard is all the way down to Kodiak unless things have changed....and that is a very long wait for them to show up to winch you up out of the water. Likewise....waiting on a Supply boat out of Nikiski to the south would be a long wait too. Perhaps some fishing boats might be in the area....but don't count on it.

In a non-float equipped helicopter....I much preferred to take the Chicken route.....go northwest from Anchorage and cross over the skinny bit then head on down to the Pass.

As the only other noise you might hear being a big bang or similar one time sound as you have a catastrophic failure of the gear box.....worst case scenario.....as low as you can get to the water.....and at a forward speed that will ensure you survive a collision with old Ma Earth.

As the Cops say....."Speed Kills!" Speed horizontally and vertically counts in this equation.

A Chip indication all by itself is not something to get too concerned about. Add in Oil Temp or Oil Pressure changes then yes.....it is a serious situation. When it comes to a MGB problem.....one with multiple indications....procrastination is not recommended. Park it like a Woman in a Shopping Mall on Sale Day! Anywhere, any way....but do so quickly!

Know how your Gearbox measures Oil Temp and Pressure.....and how the system will react to a loss in fluid contents. It might be with a loss of fluid the Temp Sensors will not accurately sense the correct Temp and thus give you a false reading. Likewise, pressure may stay in the normal range until the fluid gets so low that pressure is affected.

Any sudden increase in sound or vibration.....even absent other indications.....I land immediately. If you can hear the change in noise and feel the difference in vibration....that portends trouble of some kind.

I complained about a transmission and was told I was just getting paranoid. When I insisted and the engineers split the case on the gearbox....we discovered two bolts lying in the sump where they had backed out of the gear and thus caused an out of balance situation strong enough to be heard. In that case I was very lucky that I was hard headed.

[Hedge36]

George, you still flying out of Homer? I used to be based in Nikiski (grew up there) and have run through this scenario in my head more times than I care to contemplate :)

[170']

Hey George

It's really one of life's ponderable issues. I've had many chip lights from xmsn-trgb's-engines etc and still can't help with a definitive answer. just food for thought.

1) A low time a/c will often produce fuzz alarms
In your case I would (uncomfortably) continue monitoring temp and pressure for backup confirmation of a developing problem (or not) I would be descending to a height where I can get it on the ground/water quickly, very quickly; while looking for an LZ.

Over land: Land as soon as possible and pull the chip plug. Fuzz is clearly fuzz; clean the chip plug on a clean cloth. Tear a chunk of your t-shirt if that's all you have, and keep the rag and fuzz. With a new a/c they may want to analyse it (soap test etc) for warranty purposes.

Over water: I'd look for any land mass, boat, rig, floating debris: anything that could get me out of the water after a forced landing (not an auto,more on that later) I know the region well and although it's not arctic, as SASless suggests, it's still not survivable for long at any time of year.

If I was lucky enough to find a boat etc, I'd hover really close to get their attention and see if it develops at hover power (expect a temp rise in prolonged hover - but at the first sign of pressure falling off or any noise developing I'd put it in the water next to the boat
(A big boat and I'd drop in for coffee if they had enough deck space)

It would be nice to have all the emergency gear on board but realistically it seldom happens with light singles. I'm presenting a scenario where you're not supported by a large OGP audited operator who gives you all the advantages (sometimes;-) and as we used to say back in the day.

'Better to beg forgiveness than ask permission' in reference to landing on the boat ;-)

In the case of a machine that's had a hard life in RHL type work. all the (possible) fuzzing associated with new components is highly unlikely and typically means someones likely to have a bad day.

You if you continue...Or the mechanics when they have to figure out how to get to the typically inhospitable and unreachable area you parked the bastard.

I have many mechanic friends and many of them need exercise more than I need a catastrophic tranny failure in flight :O
...

Specifically xsmn chips:
There's many opinions on this issue and some are aircraft specific: Some people believe dry running bench tests demonstrate x minutes of endurance with no oil just to give one example. The legitimacy of these tests can be argued forever; with no firm conclusion on my part...

And there's plenty of metal chunks in the xmsn that can come apart with plenty of oil available.

The one thing I decided years ago was if a genuine xmsn issue occured; I would under no circumstances reduce power lower than needed. I would drive it under power to a forced landing at the first survivable area.

Reducing power while trying to find out what's actually happening is another issue. I'm only talking about the no oil press/high oil temp/weird noises situation.

Just one more opinion...

Keep safe....170'

[SASless]

I have many mechanic friends and many of them need exercise more than I need a catastrophic tranny failure in flight

When it comes to a mechanic (engineer) climbing a mountain with a tool box tucked into his hip pocket......or me setting on the ground with a cup of coffee saying "Sorry-O!"......as 170' rightly says....guess which one wins!

Granted the one time this sort of thing happened....it was because the aircraft would not start and was put down to a dead battery. The Engineer and I toted a battery.....one of the bulldozer sized things the Alouette III required....up a mountain to where I left the helicopter when it would not start. When I gave it a try before we changed the battery.....she fired right up.

Said Engineer said that except for me having carried half the battery up the mountain with him.....it would have been a fatal event.

[WASALOADIE]

As 170 says, there is a theory that you should keep some power applied and not reduce it below what is ideally needed. This keeps the engine(s) driving the gear train, whereas reducing or dumping all power means the gears mesh on the opposite side of the teeth or reverse loading on the gears and may lead to a power off failure of the components and seizure, power on will at least be under load from the engine forcing the gears to turn and hopefully also the pumps pumping.

[GeorgeMandes]

Thanks for all the helpful responses. Very interesting the idea of keeping high power until reaching the ground.

Interesting choices on best airspeed and altitude to fly after the transmission chip light, while over an unsuitable landing spot. I get low in altitude, but it seems a tradeoff between going very slow, and taking forever to reach shore, and going like a bunny to minimize time over the water.

Homer to Lake Clark is a regular trip, and it is 99 miles in perfect weather that allows you to go direct, a bit more for low weather with some deviations, but 160 miles around by Kenai which cuts the over water time, while requiring a refueling, and exposes you to a lot more traffic.

[skadi]

Very interesting the idea of keeping high power until reaching the ground.

No high power, but more than no power!

skadi

[Shackman]

And don't assume the lack of a chip light means everything is OK. A good few years ago the crewman at the rear of my Chinook told me there was a 'funny whine' coming from somewhere in his vicinity (and please no cracks re crewmen - they're all too obvious); if he wasn't happy I wasn't either, and we were also over a large expanse of water, so immediately ran downwind at constant power to the nearest available landing site. No chip lights, the T's and P's were also stable, but the noise from the rear transmission got louder until we could hear it at the front, and ditching was becoming an option had we not been less than 2 mins from landing. On pulling the ECLs back (ie reducing power) after touchdown it was like applying the rotor brake - hard - and when the engineers pulled the mag detector it was like a christmas tree, covered in iron filings and meatier chunks of transmission. Why no Chip Light? - no idea, the plug worked perfectly under test, and god smiled on us.

170 and Wasaloadie are quite correct - keep the power as stable as possible and get on the ground ASAP. Always remember it's better sitting on the ground looking at a broken aircraft than sitting in a broken aircraft watching the ground coming to meet you.

[oldbeefer]

Shackman.

Would this be a good time to mention the wrong hands demo?:E