01 June 2005

Let's fly!

I learned to hover a helicopter in February of 1968 in Mineral Wells, TX.

In Army uniform......flight suit, boots, helmet, and sunglasses, I got hot enough from the concentration and exercise that sweat flowed from my scalp down the front of my face and into my eyes.........and down the back of my scalp, continuing down the valley of my back, and into the fissure where the sun doesn't shine!
It IS that difficult!

I was surprised though, when the instructor got the aircraft stablilized in flight, to find I could make the machine do what I wanted it to do!

So........we've learned to hover. Now it's time to go fly!

Getting the helicopter airborne once you're comfortable hovering, is actually fairly easy.

Which direction is the wind coming from? Point the nose thataway!

Now, check your power level. In a helicopter powered by a reciprocating engine, this means looking at your "manifold pressure" gauge.
In a turbine powered machine, power is normally measured in torque (twist) applied to the drive train, and is indicated on the "torque" gauge.

So in the R22, we check the manifold pressure gauge. A common hover power setting here locally is 23 inches of manifold pressure, (MP). Remember this value, because we'll use it most of the way around the traffic pattern.

Okay, our nose is into the wind, we are at a stable 5 foot hover,
using 23" of MP.
Lower the nose of the machine just enough to start moving forward. DO NOT dump the nose over like you see in TV shows or movies! If you have an engine failure with your nose in that attitude, you'll have a Dickens of a time trying to keep from spreading the helicopter over half a city block!

Allow the helicopter to slowly accelerate while maintaining 5 feet of altitude. Use extra collective only as needed to keep the machine 5 feet above the ground. Keep the nose pointed into the wind with the Tail Rotor pedals. Insure the machine is moving straight ahead with the Cyclic.

At about 10-15 knots of airspeed, the helicopter will begin to accelerate into air that has not been disturbed by the main rotor taking big bites of it and forcing it downward. The helicopter will have a natural tendency to lift it's nose as it encounters this clean air, (the main rotor in front is working more efficiently than in the rear), and you must keep the nose from coming up, because if it comes up, the helicopter will come to a stop!

This point of accelerating into clean air.......transitioning from hovering flight into forward flight, announces itself with a mild vibration in the aircraft as the main rotor moves completely into "clean air". This transition is called "translational lift".
Translational lift is that additional lift, or efficiency, the helicopter gains by having the rotor operating in undisturbed, unaccelerated, air.

With the rotor fully in undisturbed air, the helicopter will actually fly with less power than required to hover!

The machine will get more and more stable as you accelerate because of the stability provided by increased airflow "weathervaning" the helicopter.

In the R22 we climb at 60 knots indicated airspeed. At our local elevation, 23 inches of manifold pressure at 60 knots indicated normally results in a rate of climb of 500 to 600 feet per minute.

Let's make one circuit around the traffic pattern.........
Climb straight ahead until we reach an altitude of 400 feet above the ground, then turn 90 degrees to enter "crosswind" leg. On "Crosswind", we continue holding our manifold pressure setting and indicated airspeed until we reach 800 feet above the ground, then we make another 90 degree turn to parallel our takeoff course in the opposite direction. Since we took off into the wind, we will now be "downwind".......therefore this is our "Downwind" leg. We still maintain our power setting, 23" MP, but we lower the nose to maintain our 800 feet altitude above the ground and convert the power we were using to climb into airspeed.
The R22 will accelerate to 80-85 knots indicated on downwind leg under these conditions.

And now, you are flying.

Now, all we have to worry about is getting this symphony of moving parts safely back on the ground!

Next, the "Normal" approach!



Mike said...

I have a private pilot license with about 70 hrs TT SEL.

I have four hours logged time in an R22 with a VERY patient instructor ;-)

I also have a couple of hours of 'unlogged' and 'unofficial' time flying a twin-turbine.

A pilot once told me that flying a helicopter requires the same amount of dexterity as standing on a basketball while balancing a tray with a marble on it.

I love playing around with the helicopter models in MS Flight Simulator 2004. I have flown with a couple of 'virtual airlines' doing heavy iron and simulated medevac.

My favorite is an EXTREMELY overmodelled AS365 Dauphin. It is a blast to fly. The engines have been modelled in such an extreme way that pulling full pitch results in an immediate several thousand fpm zoom climb at incredible speed.

It also allows unreal aerobatics such as are flown by RC helicopter pilots. Loops, rolls and hammerheads galore!

Anyway, I digress. Thanks Graybeard for the awesome time in the R22. I learned the best (and simplest) nav trick I have ever heard from him.

When you are on course, pick out something on the horizon and fly to it. So simple and obvious, yet I was too naive to think of it. I always 'flew the compass' with sweaty hands and sectional on my lap!

Oleprairiedog said...

Symphany of moving parts????
A more apt description might be " a nefarious multitude of moving parts in close formation".