The great Helo debate

[PhrogLoop]

PhrogLoop can probably provide better stories, but I've heard of Phrogs taking messenger lines for the RAS through the arc and rappel lines that have gotten wrapped up on the pitch change rods (or links or whatever the phrog called the connections from the swashplate to the blades).

I remember when I was at Chambers one of the local crews chopped up some firewood settling into Peanut (a small CAL zone perfectly shaped for our tandem rotors) and they were fine.

One time I was FCF'ing in the Gulf of Aden and our rear drive arm link (scissor assembly) came apart because of a missing cotter pin through the bolt after the retention nut. The aft rotor system literally settled onto its own pitch links bent to about 70 degrees instead of vertical so the aft blades went to 3 degree pitch and unresponsive. My classmate and copilot was at the controls at 70 kts /300 ft and we went uncommanded nose up and he jammed the cyclic almost into the instrument panel with no response. It must have looked like an agressive quick stop from the boat (we were 3 miles in port delta) and we started falling ass first toward the Gulf. I remember 45 degrees nose up and increasing when I took the controls, and bottomed the collective hoping we could settle into ground effect which we did...at 20 feet. We bounced around for a few seconds and my crewmen asked "WHAT THE F WAS THAT!?" and announced that they had been strapped in with the emergency egress windows gone by the time we started settling. We creeped back to the boat at 200 feet/40 knots (couldn't get any higher or faster) and got the emergency straight in to spot 8. Landed, shut down, and kissed the flight deck.

I love that ugly, leaky, smelly, underpowered battle ax because she brought me home.

 

[RobLyman]

Funny you say that, I thought the exact same thing.....

I asked an Army aviator what happened to those two guys, apparently the other guy (the one of little faith) was acutally the CO if I understood correctly and well, they both got hammered for it. I'll have to ask my friend again, as they were briefed on that incident regarding how it relates to CRM.

I know the guy (PC) and just finished a deployment with him. He is an HH-60M pilot now (CW4).

Funny story...we were all (including him) standing in a circle talking about something when a subject came up...can't remember what it was...but it lead to someone saying the quote, "He who is without sin cast the first stone" or at least that was the quote that was applicable to the conversation. However, it came out, "O ye of little faith..." then the guy trailed off and realized what he was saying.

Everyone was silent for that awkward 1-2 seconds and I had to do everthing I could not to burst into laughter.

The guy is really a super nice guy. I did some low level NVG stuff with him in Ft. Hood before deployment, but other than that I haven't flown with him.

 

[phrogpilot73]

I remember when I was at Chambers one of the local crews chopped up some firewood settling into Peanut (a small CAL zone perfectly shaped for our tandem rotors) and they were fine.

Where's Peanut? Felker's getting kinda old...

...Landed, shut down, and kissed the flight deck.

This story sounds familiar, I seem to remember reading a HAZREP about it - and the general consensus was "Holy shit, they got it back on the fucking boat?!?"

I love that ugly, leaky, smelly, underpowered battle ax because she brought me home.

Hater's just don't know...

 

[BACONATOR]

I remember when I was at Chambers one of the local crews chopped up some firewood settling into Peanut (a small CAL zone perfectly shaped for our tandem rotors) and they were fine.

I love that ugly, leaky, smelly, underpowered battle ax because she brought me home.

Yeah I remember reading in Chickenhawk about how the Huey had such a high inertia rotor-head, they'd frequently drop into CALs that were too small and just chop up the brush/branches.

Try doing that in a low-inertia bladed bird like the 60, and ....well.... I read a mishap report in recent years about an East coast squadron that did it. It doesn't end well. Those hollow tip caps don't do well against tree branches.

 

[helolumpy]

Yeah I remember reading in Chickenhawk about how the Huey had such a high inertia rotor-head, they'd frequently drop into CALs that were too small and just chop up the brush/branches.

Try doing that in a low-inertia bladed bird like the 60, and ....well.... I read a mishap report in recent years about an East coast squadron that did it. It doesn't end well. Those hollow tip caps don't do well against tree branches.

I don't think the design of the head (low-inertia vice high-inertia) is the overriding factor, it's the design of the blades. The Huey blades we designed with the ability to be able to clip branches and keep on smiling.
The H-60 was designed to lose the tip cap in the event you hit something.

 

[707guy]

Yeah I remember reading in Chickenhawk about how the Huey had such a high inertia rotor-head, they'd frequently drop into CALs that were too small and just chop up the brush/branches.

I was thinking of that from Chickenhawk while this discussion was going on as well.

 

[BACONATOR]

I don't think the design of the head (low-inertia vice high-inertia) is the overriding factor, it's the design of the blades. The Huey blades we designed with the ability to be able to clip branches and keep on smiling.
The H-60 was designed to lose the tip cap in the event you hit something.

Maybe so, but my Enginerd hypothesis is that if the H-60 hit a tree branch, bad things would happen quickly (ie: Nr would decay QUICKLY, and the blades might come apart quickly, being hollow and nitrogen-filled), whereas the high inertia of the huey's head allowed it to plow right through branches and not even slow down.

They said that in a Huey, you could twist to idle, pick up into HIGE, do a 180 pedal turn and set back down, before Nr decayed very much. Now those are some HEAVY blades.

 

[lowflier03]

Low inertia head has nothing to do with surviving tree strikes. The engines will keep Nr where it needs to be. Plenty of 60's have hit them and kept flying minus a foot or so of blade. What usually happens to make it really bad is hitting something solid enough to completely shatter the composite around the core, or tear the tranny up. But then again, all helos have to worry about that problem.

 

[BACONATOR]

Low inertia head has nothing to do with surviving tree strikes. The engines will keep Nr where it needs to be. Plenty of 60's have hit them and kept flying minus a foot or so of blade. What usually happens to make it really bad is hitting something solid enough to completely shatter the composite around the core, or tear the tranny up. But then again, all helos have to worry about that problem.

Survival is one thing. But routinely doing it with minimal blade damage (relatively speaking, in vietnam), is another. And Nr can certainly decay if the blade hits something solid enough that it doesn't have enough inertia to keep spinning. The freewheeling unit will allow the engines to keep turning at their normal Ng whilst the blades slow as they bog down on the shrubbery...

 

[Jim123]

The freewheeling unit will allow the engines to keep turning at their normal Ng whilst the blades slow

I think you might want to review your systems, in particular the engine and transmission.

 

[BACONATOR]

I think you might want to review your systems, in particular the engine and transmission.

If the engines turn while the rotor brake is on, I'm pretty sure the freewheeling unit might slip a bit, as the trees create an unnatural "rotor-brake". Forgive me, but NATOPS doesn't talk much about blades hitting trees in Chapter 2.

 

[Pags]

The freewheeling unit only decouples when nr>np. When they're running the motors are only going to droop due to tgt limiting. The rotor blades may have a hollow spar, but it's a titanium spar.

A few years ago an mh-53 had a blade catastropically fail while in flight around Norfolk. They landed safely, but the blade had a huge chunk missing from the trailing edge.

I'd tend to think that you'd be better off routinely avoiding trees then routinely trying to use your aircraft as a hedge trimmer. I doubt very many of us will ever be in the place where we'd need to put the rotors into trees once, let alone routinely. Bottom line is that if you accidentally brush into some trees, chances are the bird will bring you back home, despite your best efforts.

For what we need the 60 to do we're better off with a low inertia head. Being able to do a 180 in a cut gun without drooping is a neat trick, but is kind of useless in practice.

 

[BACONATOR]

The freewheeling unit only decouples when nr>np.

Maybe I'm misunderstanding something. Rotor Brake Start: Nr=0. Np>0. Explain.

 

[Jim123]

If the engines turn while the rotor brake is on, I'm pretty sure the freewheeling unit might slip a bit, as the trees create an unnatural "rotor-brake". Forgive me, but NATOPS doesn't talk much about blades hitting trees in Chapter 2.

Otto, I don't think the freewheeling unit works like the slipper clutch in an electric drill. Even if it does, it doesn't have much anything to do with Ng.

 

[BACONATOR]

Otto, I don't think the freewheeling unit works like the slipper clutch in an electric drill. Even if it does, it doesn't have much anything to do with Ng.

I see what you're saying, and we're getting WAAAY into weeds, but now I'm curious. I know... Ng has nothing to do with the freewheeling unit, so at what point does it allow the engine to spin freely with no regard to Nr?