Thursday, December 23, 2010

The Hover

Hey Everybody! I know it has been a while since I did an article... but I'm going to get back in the groove of things now. Here is an article on the Hover.

The Hover is a fairly easy maneuver that can be performed with almost any airplane with enough power, and more important... altitude! The hover is a high alpha maneuver in which the wings are producing no lift what-so-ever; so to do this maneuver down on the deck, you need an aerobatic airplane with lots of power. Although I was able to hover my LT-40 after I soloed, I did it at 200+ feet at full throttle and did an ugly looking hammerhead to exit. These conditions are not ideal.

Ideal conditions would be an aerobatics airplane of the "beater" classification (your backup plane that has loads of power but you don't mind stuffing). To learn the maneuver, start with an aerobatic airplane such has an Extra, Edge, Velox, MXS, or Funtana/Katana. For power, you want more than enough. A 2:1 power to weight ratio is adequate. Remember, this maneuver has the plane at zero airspeed, zero groud speed, with the nose up at 90 degrees... so you need enough power to punch out vertical whether you screw up or are just looking to exit the maneuver.

For learning, I recommend an electric airplane of the 48 inch wingspan range. This ensures that the power system will be relatively cheap, yet powerful; the airframe is cheap, therefore disposable; and small enough that you can take multiple planes to the field. This way you can practice hovering with your beater and fly normally with your sweatheart primary airplane.

CG is another thing. Find a neutral CG, meaning, set your CG so that no down input is needed during inverted flight at half throttle. The model should not climb while inverted either. It will take a few flights of experimentation, but once you get it right, you'll plane will fly awesome.
Ok, enough preperation, let's get to the flying! Again, start high so you have room to pull out if you lose orientation and have to let the plane fall. Also it helps to be up high so if you add power to pull out, you don't end up hitting yourself with the plane as it flops around at 4 feet off the deck.

To start, fly along on the far side of the runway at your desired "up there" altitude. Then, simultaneously pull the throttle back and pull full up elevator. Once the nose rises to almost 90 degrees, add power, but not full, just increase it a little. This maneuver requires a lot of "feel" for your aiplane, so if you feel it needing more power, add it, if it needs less, take it away.

For starters try to find a throttle position that holds your altitude without climbing or decending. Once you have found a throttle position, move your control surfaces accordingly to keep the nose straight up and the canopy facing you. You will soon find that your throttle needs to be worked almost constantly to establish and hold your desired altitude.

Now that you have a feel for your control inputs and throttle movements. Bring it a little lower. When I was learning, my prefered method of entry was as follows:
Step 1: Get up high.
Step 2: Chop Throttle.
Step 3: Roll inverted and pull to do a Spit-S.
Step 4: Leave your throttle at idle as you travel down the runway.
Step 5: As the plane passes you, bump full throttle and full up elevator at the same time.
Step 6: Immediately chop the throttle after the full throttle bump.
Step 7: Feed back in throttle (another burst to full is probably needed), then adjust throttle and controls to maintain your desired altitude and attitude.

This entry is known as the "Wall entry" because you are doing a wall to enter a hover.

The main thing to remember with this maneuver is this, if the plane falls to the right, add left; if it falls left, add right; if it falls down, add up; if it falls up (towards the canopy), add down. With any major pitch correction, be sure to bump throttle with the control input to throw air over the surface. Vectored thrust plays a big role in this maneuver because the only air moving over the control surfaces is that provided by the propeller.

Again, feel is the key. At first, people tend to overcontrol the airplane. This is good... sort of. It is good because at least you give enough to keep the plane from driving itself into the ground. It is bad because it may throw the plane into the other direction leading to a series of unfortunate events eventually leading to a crash. Make sure your controls are adequate enough to stop the plane from falling out of the maneuver, but small enough to keep it from falling in the other direction. Your control surfaces should have about 45 degrees of throw for adequate correction and maneuverability. It takes practice, so don't get discouraged.

The hover is basically lots of control inputs given to counteract the motion of the plane in an unwanted direction. Soon, your control inputs will be minute and precise enough that the plane won't look like it is jumping around like it just got attacked by a mound of fire ants.

One last thing, entry is everything, if you don't enter correctly, you are going to have a hard time getting your hover to look good.

Here is a training video I made:

Hope this helped! -Tom

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