All Things Aviation Related - Page 97

svandamme · svandamme's Garage

Quote:

Originally Posted by Seahawk

I'mmm baack

The key is you cannot separate main rotor performance and tail rotor performance in terms of power available and power required. They are as one. I would get finger cramps trying to explain "power settling", "settling with power" and any of five other dynamic flight states that keep helicopter pilots awake at night.

Yeah nah i get that, but my question was, clearly not a point in this case by KNS's comment..

What if , max power, and you are at max tail rotor pedal
And suddenly the main rotor would find itself in ground effect

I mean I get that its near impossible on a big flat normal ground surface, because well, everything is even.

But lets suppose you "could" get into ground effect, as you approached a landing spot on a cliff (or lets say a ship's deck)

The helo approaches, HEAVY
and really short, barely any fuel was burnt off
And for some freaky reason, air pressure did a big drop Don't ask me why, but for arguments sake it did

barely flying, it has enough lift because it has forward velocity
The darn thing is already very high on the collective
add a bit of wind and tail rotor pedal is already close to max

1 as it slows down , you'de need more power to flare and transition to hover? yes?
2 That will need more tail anti torque to keep from spinning so now we are at max pedal input? yes?

Ok, again, I know this is all not entirely realistic, Its a what if for me to understand what those things do (without having option to go fly one), and

as it then enters the hover, and suppose that ground effect does kick in
3 Would the ground effect that gives additional lift, not also require more anti torque
eg the rotor has more grip on the air, so the reverse torqe on the fuselage increases?

4 Would that same thing, the ground effect, at the same time make the tail rotor more effective, or could there be a scenario that the tail is so long , out over the edge and the ground effect just vanishes there.

Seahawk · 10-07-2022, 10:08 AM

https://www.thehelicopterstudyguide.com/how-does-a-helicopter-perform-in-ground-effect-vs-out-of-ground-effect/

The positive effects of IGE hover vary from helicopter to helicopter and are, as we have discussed, also dependent on DA, helicopter weight, wind direction and speed, etc.

There are many different rotor and tail rotor designs so IGE hover decrease in power required advantages vary. I don't have my old NATOPS manual handy but in the SH-60 I think the IGE gave you 2-3% increase in efficiency.

3 "Would the ground effect that gives additional lift, not also require more anti torque eg the rotor has more grip on the air, so the reverse torqe on the fuselage increases?

No. Any reduction in power required, a benefit of IGE hover, reduces, in the broad sense, anti-torque requirements.

4 Would that same thing, the ground effect, at the same time make the tail rotor more effective, or could there be a scenario that the tail is so long , out over the edge and the ground effect just vanishes there.

Again, different designs, combinations of main and tail rotor criteria (blade cord, type of tail rotor, etc.) can have varying degrees on efficiency IGE. Many books have been written.

The 60 tail rotor, for instance, is canted and helps with anti-torque efficiency in certain flight profiles:

So is the 53E:

But if you look closely you can see the difference.

The Huey in the video does not have a canted tail rotor.

All of that said, the tail rotor doesn't "see" IGE, all the machine knows is that less power is required across the spectrum.

svandamme · svandamme's Garage

thanks !!

KNS · 10-07-2022, 11:01 AM

Svandamme,

you're combining several different scenarios that may or may not all be happening at the same time.

It's rare to hit "max tail rotor pedal" as in hitting the physical limit of a pedal's travel, at least in the aircraft I've flown. You might touch it ever so briefly while extreme maneuvering in a hover and/or encountering strong gusts while hovering.

If you're coming into land and you push in a whole lot of pedal at the bottom of the approach, it's because at the same time you're pulling in a lot of collective/power. As Seahawk stated the power available to the main and tail rotors are interconnected. application of either one affects the other. Or, if you're pushing a whole lot of pedal to arrest a large yaw (a huge gust of wind), it's also going to drag down main rotor RPM a bit. In a hot and high situation the problems are multiplied.

Ground effect does give a little extra to your hovering performance but there's other factors affecting the performance of the tail rotor, whether its in clean air or not.

When you move from a no wind hover into forward flight, you'll be leaving that area of ground effect and find a momentary need for additional power (which will require a little bit more pedal). Very quickly after that you will fly through Effective Translational Lift (ETL) and the aircraft will experience a slight aerodynamic gain allowing you to reduce power if you desire.

That scenario plays out in reverse as you are on approach coming to a stationary hover (in a no wind condition).

Throw in gusty wind, high DA, a pinnacle landing and that all affects how much or how little you apply collective and TR pedal.

Racerbvd · Racerbvd's Garage

GH85Carrera · GH85Carrera's Garage

STILL the fastest! Pete Knight flew the modified X-15A-2 to its maximum speed of Mach 6.7 or 4,520 mph, still the fastest anyone has ever flown an aircraft. Shock waves from the record-breaking speed resulted in considerable heat damage to the aircraft and the X-15A-2 never flew again.
October 3rd, 1967, "Pete" Knight gave that Ol' Mach Demon the best chase it ever had! A speed record that still stands to this date. Knight also became one of only five pilots to earn their Astronaut Wings by flying an airplane to an altitude over 280,500 feet.

Sooner or later · 10-08-2022, 12:45 PM

Hell of a ride. Parachute required.

t6dpilot · t6dpilot's Garage

How’d you like the ride? I got a ride in Jackie C years ago and boy that back seat made me feel claustrophobic. I kept wondering how the heck am I going to get out if I need to. The pilots seat back came out so I could get in. Then once reinstalled, it was literally in my lap. Makes the hairs on the back of my neck stand up thinking about it.

My old bird with a fresh paint job. Scraped all the old cracking paint off and reapplied new paint. Looks awesome. Love that airplane.

svandamme · svandamme's Garage

that is awesome !
got video?

Sooner or later · 10-08-2022, 04:18 PM

Quote:

Originally Posted by svandamme

that is awesome !
got video?

Not any that I took. My sister took a ride, too. She took some short clips. That image is a screenshot from one of her clips.

Sooner or later · 10-08-2022, 04:29 PM

The ride was great. He kept us up for about 30 minutes. I am just at 6'4" and I had plenty of room. Headroom was tight. To make room for the passenger seat they removed radio gear and a gas tank that was originally behind the pilot.

He wasn't allowed to go inverted, though he did put it through some nice 3+ G maneuvers. Quite a few lazy 8's.

Pilot was ex air force and now flies commercial.