Official Helicopter Enthusiasts Thread

flat pitch is flat pitch, there is no special "below 0*" pitch or collective position for such. (at least for the 5 army a/c i know of)

 

Wrong. The Lynx has the ability to have negative pitch. The blades can be feathered past zero pitch to induce lift upside down basically. The "upside-down" lift allows the aircraft to hold tight on a rolling ship up to 40 degrees.

 

gotcha, i can only speak for army (US) choppers.

I have a friend from the unit I just left thats an Ausie lynx pilot. Ill have to call him up and ask bout that, never knew about it. Id like to see what he has to say about the science and how it works

 

Cool. Yeah I believe the collective can be pushed down through the normal stopping point to invert the pitch on the blades. Not sure if all Lynx do it, may only be the naval ones.

 

Photos my dad sent me today from Volusia County Sheriff, Deland, Florida.

 

I think negative pitch is a matter of perspective... it depends on how the mechanic rigs the pushpull tubes. In the army every six month the helo's got a autoroational setting which changed with the average air density of the season...so that flat pitch resulted in a generally sustained RPM in autorotation. Once I became civilian i noticed then mechanics no longer reset the main rotor pitch for the season, so depending on air density, it becomes very easy to overspeed a rotor in autorotation, but also easier to regain low rotor.

I have no first hand experience of the lynx other than hearsay from others that have flown it that say it is incredibly manueverable, but I would reckon that negative lift would be a fairly dangerous thing to play around with since the rotors would cone down into the tailboom and would make entry into autorotation pretty unnerving. If the royal navy indeed puts negative lift on the blades I wonder how they figure enough is enough. Very curious.

All the navy helos I've heard about landing in rough seas would hook a winch cable up to the cargo hook and winch the helo down as the pilot maintained tension with positive lift.

 

@TXSmiley , you have a new thread to check out.

 

We don't set rotor RPM in an auto for the season, we fly in to many different areas for that to make sense. When the aircraft is track and balanced it is usually checked and set then.
With regards to the negative pitch you can use in a LYNX for example (others do it too) it requires a hefty push downwards on the collective when on the ground to put the blades into negative pitch. Not something you could really do in an autorotation situation. It is actual negative pitch (the EH101 can go as much as -10 degrees as far as I know) to suck the aircraft into the deck when needed in rough seas etc.
Usually the collective isn't fully down in an auto, especially in turns etc where you need to control the RPM.

 

I see what youre saying, and i get it but I wonder what effects that has on droop stop pounding. displacing the cyclic "full forward" (or any forward) with no power (let alone "negative" power, or collective) would be thrusting the pitch housing down (forward in this case) and smashing the bearings. I wonder what they do to counteract this or protect against it (unless it just means more wear and tear on components)

 

That video has me thinking....

A heli pilot, when hovering has to keep his head still, using peripheral vision to keep the machine from tilting or wandering.

Now when the pilot in the video was working the landing, I would think he has to disregard the pitching and rolling ship and concentrate on the horizon to keep the heli level..... but then keep a third eye out on the pad as he gets near touchdown.

I was watching the the cyclic inputs the pilot was adding as he was over the pad.... Is/was that flown by hand?... or is the some kind of gyro stability system to aid in landing, especially in the conditions he was in?

 

I thought every helicopter can go to a negative pitch?
From what I understand, executing an autorotation requires the blades go negative to aid in maintaining the rotorspeed as the machine descends.

 

No they don't go negative. There may be a slight negative degree at the tips but in general that blades are always at a positive or flat pitch. You use the collective to adjust pitch to maintain rotor speed. You need that positive pitch creating drag to slow the rotor RPM down if it accelerates while maneuvering in the autorotation. As I said in the earlier post, there's usually some collective being applied throughout the maneuver.

 

We don't have to keep our head still while hovering. I hover looking sideways and down at the ground for most of my hover time, and I do it a LOT, checking guages etc every now and again. Yeah, looks like its all flown by hand.

 

It doesn't have a fully-articulated rotor head, it has a rigid rotorhead.

 

yes...disregard the ship and look at horizon. exactly. Like irish carver said though its not that you have to keep your head still, you just use the correct reference points. As far as autopilot vs handflown, IDK for sure but I would suspect hand flown, autopilot's usually don't have that much control authority. But yes most twins have some sort of stability augmentation (usually called SAS/SCAS) but I don't think you can see the results of it's use in airframe movements. It's usually the other way around; when flying without SAS the airframe looks like it's getting overcontrolled, when it's on the airframe is rock solid.

most blades that I know of have a slight "twist" to them. Aerodynamically the relative wind on the blade is different at every radius along the blade which changes the lift vector along the blade as well. When pilots refer to "flat pitch" usually they mean collective full down, but whether that is actually flat pitch per se is a matter of rigging the flight controls and where you measure along the blade.

 

News of a medical helicopter crash outside of Phoenix. Hope and pray for the crew and that any of our TW friends were not involved!

 

Worked on this bad boy for 6 yrs. AVNX and Armament. Man I miss working on helicopters. I enjoyed it way more than working on airplanes.

 

That's awful, another one. A friend of mine was killed in the one in Cali last week. Sucks!!

 

Sorry to hear. You know as well as I do the flight community is fairly small. If you're in it long enough, It may hit close to home eventually. I've lost 3 crew members myself. Last nights crash was my friends' aircraft. He was off duty, but the crew that was on, he regularly flew with. God speed to all those involved and their families.

 

yes, thoughts and prayers to the family and GOD speed to those involved.