Silencing Rotor Blades

[RobLyman]

Army UH-60M is out with them on the new wide cord blades to increase lift, nothing to do with "sound".

They do make a slight difference in sound. You can usually tell the difference between an A/L and an M out on the flight line. The difference is not as dramatic as on the video/link.

Oh, and YES, the M has a rotor brake. After flying the Seahawk, that is one the thing I think I missed the most when I started flying the Blackhawk.

Here is a bad cell phone shot of the wide chord blade on the M model.

 

[lowflier03]

They do make a slight difference in sound. You can usually tell the difference between an A/L and an M out on the flight line. The difference is not as dramatic as on the video/link.

Oh, and YES, the M has a rotor brake. After flying the Seahawk, that is one the thing I think I missed the most when I started flying the Blackhawk.

Here is a bad cell phone shot of the wide chord blade on the M model.

That blade design is similar to the 60Ks I've seen. However the Japanese have added some of the design elements from the first picture. Their tips actually sweep a little forward before dropping down and sweeping back.
Though I never heard an actual number associated with the noise decrease. They did claim a significant decrease in Tq requirements for both hover and forward flight.

 

[Gatordev]

And a gust lock! Which is for god knows what...(I think it's an Army thing).

Do Sierras not have Gust locks? Or am I misunderstanding your post. I always thought it was pretty integral to automatic blade fold, so not sure why it would be an Army thing.

 

[exhelodrvr]

And a gust lock! Which is for god knows what...(I think it's an Army thing).

Keeps the tail rotor from spinning due to the wind. That's an issue when the tail is folded, and the tail rotor is no longer linked to the main rotor. (i.e. with H-3s on board ship.)

 

[Pags]

Do Sierras not have Gust locks? Or am I misunderstanding your post. I always thought it was pretty integral to automatic blade fold, so not sure why it would be an Army thing.

No, we do. I was talking more about the switch in the cockpit that I've never used or heard of anyone using. Our tech rep got us some army troubleshooting pubs once and it mentioned putting on the gust lock where we would have on the rotor brake.

Keeps the tail rotor from spinning due to the wind. That's an issue when the tail is folded, and the tail rotor is no longer linked to the main rotor. (i.e. with H-3s on board ship.)

In the 60 that's what the TR indexer is for. Same idea, different name. The gust lock is a motor up by the head that moves the head to the correct position for folding. But there's a switch in the cockpit labeled "gust lock" that does something (I'm assuming). But I've never used it. Ever.

 

[exhelodrvr]

In the 60 that's what the TR indexer is for. Same idea, different name. The gust lock is a motor up by the head that moves the head to the correct position for folding. But there's a switch in the cockpit labeled "gust lock" that does something (I'm assuming). But I've never used it. Ever.

That's completely different than the H-3 gustlock. The H-3 gustlock was a metal "contraption" that the PCs would put on the tail rotor prior to folding the tail that would keep the tail rotor from rotating; it had nothing to do with the blade fold system.

 

[Jim123]

In the 60 that's what the TR indexer is for. Same idea, different name. The gust lock is a motor up by the head that moves the head to the correct position for folding. But there's a switch in the cockpit labeled "gust lock" that does something (I'm assuming). But I've never used it. Ever.

This is vaguely coming back to me (been over five years). The maintainers usually folded and unfolded the blades and the H2Ps were expected to watch or help once in a while as part of their professional development/knowledge. That motor wasn't strong enough to hold all four folded blades in position (need the rotor brake for that... think of the four folded blades like a bundle of lumber that wants to follow gravity when the ship rolls and want to swing back and forth all together... bad!). I remember the TR indexer being on the short list of things powered by the battery bus (also fire bottle CADS and nonexistent inflatable float bags)... if the indexer wasn't there to hold the TR when you fold the tail pylon then like exhelodrvr said, watch out!

Or something like that.

 

[Pags]

The TR indexer is the same idea, but more advanced. The TR indexer is a metal "fist" that extends from the tail into a crown that's around the TR. The indexer extends when the tail is cracked (but only with battery power on. bad juju if the PC forgets to turn on the battery power first). The indexer fits into the crown and prevents the TR from windmilling.

 

[RobLyman]

Ahhh...some confusion here. The tail indexer is not the gust lock. It is a cam that lodges into the crown assembly on the tail rotor, moving it to the proper position and keeping it from spinning when the pylon is folded. The gust lock on the Seahawk is a geared motor that engages the teeth on the rotor brake disc and indexes the main rotor for folding. On the Blackhawk, it is a lever type pin that engages the teeth on the rotor brake disc to keep the blades from spinning freely while unattended. It can also be used to hold the rotors from turning while operating a single engine at idle for maintenance (idle leak checks). On rotor brake equiped Blackhawks, the gust lock is only there for engine off operations (ie while it is tied down and/or unattended). The bend in the lever pin to incorporate the rotor brake on the output shaft makes the design too weak to hold against an engine at idle and a warning was added to our -10 manual (Army version of the NATOPS).

When did they take the float bags off the Seahawk? The SH-60B had them. I remember some boy scouts popping the floats at NAS Jax prior to an airshow out there when they were let onto the flight line before the crew had disconnected the battery. Sadly, they were designed to be used with helium and would open in just a few seconds; not much slower than a car's airbags. Since ship could only provide nitrogen servicing, that was used instead. Nitrogen, being a much larger element, took about 60 seconds to fully inflate the bags. BTW, if you haven't seen the video demonstration of that, the helo-on-a-stick out in front of NS Mayport was the airframe used for that demo.

 

[helolumpy]

When did they take the float bags off the Seahawk? The SH-60B had them. I remember some boy scouts popping the floats at NAS Jax prior to an airshow out there when they were let onto the flight line before the crew had disconnected the battery. Sadly, they were designed to be used with helium and would open in just a few seconds; not much slower than a car's airbags. Since ship could only provide nitrogen servicing, that was used instead. Nitrogen, being a much larger element, took about 60 seconds to fully inflate the bags. BTW, if you haven't seen the video demonstration of that, the helo-on-a-stick out in front of NS Mayport was the airframe used for that demo.

During my first tour (94-98) they removed the floatbags, I think it was in late 1996.

One of the big issues I always was told was since the bags would cover about 1/2 to 2/3 of the pilot/copilot windows (when the helo was sitting upright) most pilots briefed that they would not inflate the bags until at least one window was jettisoned.

Never being part of the discussion at NAVAIR I'm guessing it came down to the maintenance requirements against the usefullness of the float bags.

The one good thing was 'towel bar' that used to be on the aircraft. I had an AW who would ask us to set the parking brake for the main mounts and then in a hover would crawl out and knock on the pilots door. Scared the shit out of a few pilots, myself included.

 

[Gatordev]

No, we do. I was talking more about the switch in the cockpit that I've never used or heard of anyone using. Our tech rep got us some army troubleshooting pubs once and it mentioned putting on the gust lock where we would have on the rotor brake.

Ahh, yeah. Never touched it myself.

This is vaguely coming back to me (been over five years). The maintainers usually folded and unfolded the blades and the H2Ps were expected to watch or help once in a while as part of their professional development/knowledge. That motor wasn't strong enough to hold all four folded blades in position (need the rotor brake for that... think of the four folded blades like a bundle of lumber that wants to follow gravity when the ship rolls and want to swing back and forth all together... bad!). I remember the TR indexer being on the short list of things powered by the battery bus (also fire bottle CADS and nonexistent inflatable float bags)... if the indexer wasn't there to hold the TR when you fold the tail pylon then like exhelodrvr said, watch out!

Or something like that.

The blade fold process requires you to put the brake on so the gust lock isn't really an issue. It just drives the head around. I'm pretty sure the computer won't fold w/out the brake on. Then again, I haven't folded "in awhile" and my Natops is at work.

 

[bert]

The gust lock is part of the blade-indexing unit and is used in conjunction with the automatic main rotor blade fold sequence. Its primary function is to lock the rotor brake disc in an indexed position and to prevent the rotor brake disc from turning inadvertently should the rotor brake hydraulic pressure bleed off while the rotors are spread. The GUST LOCK switch, located on the MISC SW panel, manually initiates engagement of the lock. The GUST LOCK caution appears when the gust lock feature of the blade indexing motor has been engaged. The GUST LOCK caution will appear automatically during the blade fold sequence or whenever the gust lock switch is placed in the LKD position.​

And the associated caution is fair game for a checkride as well, of course.

 

[Pags]

And the associated caution is fair game for a checkride as well, of course.

But of course. My point was that I've never thrown that switch. I think it and the UTIL HYD PUMP switch may be the only ones I've never used.

 

[Gatordev]

But of course. My point was that I've never thrown that switch. I think it and the UTIL HYD PUMP switch may be the only ones I've never used.

I may regret asking this, but what's the UTIL HYD PUMP switch?

 

[squorch2]

It's used for the CSTRS (towing) system. Otherwise it's off.