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Steep Approach

This maneuver is used to transition from forward flight to a hover or a landing when a normal 10 degree approach will not clear obstacles.

Maneuver Description

Approach Angle

We usually consider a normal approach to be a 10 degree approach. More than 10 degrees is considered to be a "steep" approach. You can fly any steep angle you have the power for, up to 90 degrees. However, for the purposes of teaching we use 15 degrees as a "steep" approach.

The maneuver is similar to a normal approach except that at a given altitude you will intercept the 15 degree approach angle closer to your landing area than you would while intercepting a shallower angle. This typically requires a slightly more aggressive decelleration than for a normal approach, since you have to get rid of the same amount of airspeed, but over a shorter distance.

You will also notice that the collective will initially have to be at a lower position than for a normal aproach, and you will be holding more right pedal as well.

The approach and deceleration are exactly the same as for a normal approach, simply at a steeper angle. The controls are manipulated the same as during a normal approach.

The next big difference you will notice is that you will be at a higher altitude when losing translational lift than during a normal approach. This will require more power than a normal approach would, and needs to be included in your pre-approach planning.

Settling with Power

The steeper the approach is, the more likely the pilot is to encounter settling with power. Remember that descent rate should be below 300 feet per minute before you lose ETL (Effective Translational Lift).

A common mistake people make is to keep their airspeed high in an attempt to avoid settling with power. This actually makes things worse, since your descent rate is dependent on your ground speed. A higher airspeed means a higher ground speed, means a higher descent rate. You are actually much better to fly a slow approach in order to keep your descent rate low. The key is to make sure you decrease your descent rate below 300 feet per minute before you slow below ETL.

Common Mistakes

Failure to maintain approach angle

Until the pilot can judge approach angle accurately, he may deviate from approach angle and not realize it. While overshooting onto steeper angles certainly occurs, the more common problem is failure to increase power to account for the back side of the power curve. Especially below 40 knot, the power required increases quickly, and the pilot may simply not raise collective fast enough. If you are using a steep approach to clear obstacles, a descent below approach angle may settle you into the obstacle you are trying to avoid. Therefore it is important to immediately counter any tendency to settle with immediate application of power. This also will help prevent an entry into settling with power if airspeed is below ETL.

Failure to decelerate properly

A common mistake is to have too much air/ground speed on short final during a steep approach. This is caused by a number of things: less time to decelerate, higher altitude above terrain making the speed seem slower, fear of an engine failure. This tendency toward high speed needs to be fought. It is much better to be a little slow and have to add a little extra power to maintain altitude, than it is to be fast and have to flare. A steep approach is being used because of obstacle clearance concerns, and a flare drops your tail rotor right into the obstacles you are trying to miss.

Paul Cantrell
paul at copters.com (replace " at " with "@" to email me - this avoids SPAMMERS I hope)

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