Don't assume anything

[SpiraMirabilis]

How many of us have had the pleasure to fly "hangar queen" aircraft that have "well known issues" or quirks with perhaps a gauge or other similarly benign sounding issue?

http://www.marinecorpstimes.com/sto...aused-fatal-marine-helicopter-crash/74288256/

While the warning lights typically indicate an emergency, the pilots likely assumed the problem was due to a faulty gauge, not actual fluid loss, because of recent maintenance issues. About a week prior, their aircraft had undergone maintenance because of a faulty reading, which included replacing oil pressure sensors.

With Twentynine Palms more than 15 minutes away, the pilots decided to continue flying. They passed two airports where they could have landed safely before the transmission froze, the investigators found.

 

[Beefy McGee]

Well, I've been waiting to see the results of this crash investigation. Captain Satterfield was one of my IFS students in late 2012. He was a good guy and a good flight student. A quiet country boy from Kentucky who wanted to be a Marine helo pilot. At least he got to live it for a while. Sad to see they easily could have survived if they had only realized the true situation.

 

[MikeD]

In a helicopter, anything transmission related is normally a Land Immediately. Not Land as Soon as Possible....as in land at nearest suitable road or piece of conctete; it's land now in the safest place that's right below you.......open field, road, whatever. Helicopter pilots are eternal pessimists for a reason, as the helicopter does not want to normally fly, it wants to crash. And it will take you with it, if you let it. Plus unlike airplanes, there are far moving parts and such that if they zig when they're supposed to zag, they will tear themselves.....and the helicopter......apart. When it comes to the transmission, when/if that transmission seizes, the main rotors come to a halt and you don't even have autorotation capability anymore....you are literally an airborne brick.

Sad to see what happened. But there are certain warning lights, pertaining to certain systems on a helicopter, that you HAVE to honor, whether a past problem or not, because of the fact that if it's a real problem this time around, the fallout from failing to honor that, is often fatal.

 

[X-Forces]

In a helicopter, anything transmission related is normally a Land Immediately.

To include TRGB!!

I have had more then one instance where a MRGB Low oil pressure, TR Chip, etc have sent a chill up my spine. We had one instance where we landed in a guy's back yard on our way back to Cairns AAF.

Not Land as Soon as Possible....as in land at nearest suitable road or piece of conctete; it's land now in the safest place that's right below you.......open field, road, whatever. Helicopter pilots are eternal pessimists for a reason, as the helicopter does not want to normally fly, it wants to crash. And it will take you with it, if you let it. Plus unlike airplanes, there are far more moving parts and such that if they zig when they're supposed to zag, they will tear themselves.....and the helicopter......apart. When it comes to the transmission, when/if that transmission seizes, the main rotors come to a halt and you don't even have autorotation capability anymore....you are literally an airborne brick.

Fixed it for you.

 

[moxiepilot]

How many of us have had the pleasure to fly "hangar queen" aircraft that have "well known issues" or quirks with perhaps a gauge or other similarly benign sounding issue?
/

At the risk of sounding high and mighty, that's one of the great things about being PIC - I don't *have* to fly anything with any issues if I choose. Quirks get fixed by mx. End of story

 

[Wardogg]

Where was the enlisted voice of reason in the back of that thing? Are the Hueys not flying with an enlisted guy in the back at all anymore?

 

[Nark]

Isn' the Hawk, and by assumption (...) the Heuys main transmission certified to still work for 30mimutes without fluid?

 

[Wardogg]

“Loss of MRGB oil pressure will render the helicopter unflyable within 15 minutes,” the aircraft’s Naval Air Training and Operating Procedures Standardization manual states.

 

[Cherokee_Cruiser]

0 knowledge on Marine helicopters, are these two both considered pilots sitting side-by-side? Tandem? Both can control the aircraft or only one? Or is one a pilot and the other a non-pilot?

Also, with a complete oil loss, the main rotor blades will stop spinning and prevent an auto-rotation emergency landing? I'm just trying to envision what this would look like. Hard to imagine something spinning fast to coming to an instant halt to make it a falling brick. As long as they are still turning and swiping a bite of air, shouldn't it have enough capability to land?

 

[USMCmech]

0 knowledge on Marine helicopters, are these two both considered pilots sitting side-by-side? Tandem? Both can control the aircraft or only one? Or is one a pilot and the other a non-pilot?

Also, with a complete oil loss, the main rotor blades will stop spinning and prevent an auto-rotation emergency landing? I'm just trying to envision what this would look like. Hard to imagine something spinning fast to coming to an instant halt to make it a falling brick. As long as they are still turning and swiping a bite of air, shouldn't it have enough capability to land?

The Huey is a two crew helicopter with a Capt and FO, and usually a crewchief in the back.

The transmission turns the rotor head, which turns the rotor blades. The transmission is rated to run for a certain amount of time without any oil (15 mins in this case I believe). If the tranny seizes, it absolutely can and will stop the rotor suddenly. If that happens, it's the equivalent of the wings falling off and the aircraft literally falls out of the sky. This is why a main rotor gearbox (MRG) problem is a "Autorotate Imeadiatly" to the closest possible landing site.

 

[Nark]

0 knowledge on Marine helicopters, are these two both considered pilots sitting side-by-side? Tandem? Both can control the aircraft or only one? Or is one a pilot and the other a non-pilot?

Also, with a complete oil loss, the main rotor blades will stop spinning and prevent an auto-rotation emergency landing? I'm just trying to envision what this would look like. Hard to imagine something spinning fast to coming to an instant halt to make it a falling brick. As long as they are still turning and swiping a bite of air, shouldn't it have enough capability to land?

Yes, full rated Naval Aviators. Prior to all flights there will be a designated Pilot in Command. Just like 121. The PC can fly form either seat.

Yes, the main rotor needs to spin at nearly 100% to perform and autorotation.

The blades will continue to turn if the main transmissions seizes as there is a free wheeling unit*. Just like a pull start on a lawn mower. However once the rotors fall below ~95% (ish, each helicopter is different) there is essentially no recovering.


*proper term...

 

[Roger Roger]

How many of us have had the pleasure to fly "hangar queen" aircraft that have "well known issues" or quirks with perhaps a gauge or other similarly benign sounding issue?

http://www.marinecorpstimes.com/sto...aused-fatal-marine-helicopter-crash/74288256/

Ah, to be just a pilot and see everything in black and white.

 

[MikeD]

Where was the enlisted voice of reason in the back of that thing? Are the Hueys not flying with an enlisted guy in the back at all anymore?

Normally are for operational missions. Might not be required for non-tactical missions possibly.

Isn' the Hawk, and by assumption (...) the Heuys main transmission certified to still work for 30mimutes without fluid?

I wouldn't bank on that at all, even though there is a given time limit.

0 knowledge on Marine helicopters, are these two both considered pilots sitting side-by-side? Tandem? Both can control the aircraft or only one? Or is one a pilot and the other a non-pilot?

Also, with a complete oil loss, the main rotor blades will stop spinning and prevent an auto-rotation emergency landing? I'm just trying to envision what this would look like. Hard to imagine something spinning fast to coming to an instant halt to make it a falling brick. As long as they are still turning and swiping a bite of air, shouldn't it have enough capability to land?

Oil Loss = eventual transmission seizure = rotors slow, cone, and come to a stop = airborne brick

 

[Nark]

I wouldn't bank on that at all, even though there is a given time limit.

Just like the primary servos being rated to take a 7.62mm and continue on... I'm with you on that.

One thing I think that needs to pointed out. In the civilian side of flying, Land ASAP means just that. That includes all flying a military aviator does while in the National Airspace system (in this case.)
However Land ASAP takes on a new meaning, when the poppy field below is surrounded by bad guys, and you're doing your best to remember what the S2 brief said before the mission launched. Think Scott O'Grady.

 

[MikeD]

Just like the primary servos being rated to take a 7.62mm and continue on... I'm with you on that.

One thing I think that needs to pointed out. In the civilian side of flying, Land ASAP means just that. That includes all flying a military aviator does while in the National Airspace system (in this case.)
However Land ASAP takes on a new meaning, when the poppy field below is surrounded by bad guys, and you're doing your best to remember what the S2 brief said before the mission launched. Think Scott O'Grady.

Correct. There are new meanings to things when it comes to combat vs peacetime. Whether or not it was just a "it's the gauge again" sort of thing, or whether a "gonna be a pain to get maintenance way out here if we land here" kind of thing (or both, possibly), the result will be the same in this peacetime situation, eventually. And sadly.

 

[Cherokee_Cruiser]

Oil Loss = eventual transmission seizure = rotors slow, cone, and come to a stop = airborne brick

So then my question becomes, as the oil slowly starts to leak out, the transmission I assume starts operating roughly, and as rotors are slowing, wouldn't that be indicated by a loss of power? Which would make their predicament known, unequivocally, that a forced landing was imminent? At some point between 100% to 95%, would it be obvious? (If below 95% is no chance of flying).

 

[MikeD]

So then my question becomes, as the oil slowly starts to leak out, the transmission I assume starts operating roughly, and as rotors are slowing, wouldn't that be indicated by a loss of power? Which would make their predicament known, unequivocally, that a forced landing was imminent? At some point between 100% to 95%, would it be obvious? (If below 95% is no chance of flying).

Your first indications would be transmission oil pressure drops on the gauge; all the way to late in the game there being potential noise/grinding (not where you want to fly it to). It's not something that happens insantly or with no warning. There is ample warning. However in this case it appears the crew did not honor those warnings, seemingly choosing to treat it as a Land as soon as Practical, versus a Land Immediately.

There's not power loss from the engine(s), as they're not affected by transmission loss of pressure; the loss comes in NR or rotor speed. The engines still work attempting to turn the transmission through the high speed shafts, but the transmission with no oil is the one that hold things up and eventully fails, or snaps the high speed shafts apart in the process too.

 

[Nark]

@Cherokee_Cruiser think of the rotors like wheels on a car. The motor turns the the transmission, which in turn, drives the wheels through linkages (differential).
Now, if your transmission in the car craps out, and you lose fluid, your tires are still spinning, because of the momentum of driving. If you fail to do anything when your transmission seizes (i.e. Shift into neutral), you will come to a screeching halt.

Now, to put this in helicopter perspective, once the transmission fails, you have a very narrow window to "shift the transmission into neutral." This would be comparable to an autorotation. (Without immediate action, the rotor speed will "droop").

An autorotation is: the upwards volume of air, turning the blades. The mast/transmission is no longer providing the power to rotate the blades.
During autorotation only 25-30% of the surface area of the blades are creating lift. This is why helicopters can "glide" to a spot, rather than fall out of the sky. However, giant exclamation point!!! The rotor still needs to be spinning somewhere very close to 100% in order for the small lift, to be useful.

 

[Ian_J]

The blades will continue to turn if the main transmissions seizes as there is an interlock.

Hmmm... you sure about that?

 

[Nark]

Hmmm... you sure about that?

I'm digging in the recess of my brain. I can see the device, but I can't remember the proper name... Spline gear?


Edited to add:
After a 15 second look in the -10, it's called a free wheel unit. (2.41.1)