Sunday, 3 August 2014

Two methods, two results.

One of the manoeuvres that has moved from the “annoyingly elusive” to “adequately executed” category is my forced approaches. For two lessons now I’ve made the field each time.

To say that this is a relief is somewhat of an understatement. So what has changed in order for me to consistently carry these out effectively?  Well, since you ask, I will tell you!

To understand my answer you have to know that there are two basic methods taught for forced approaches. You don’t actually have to use either of them, if the examiner cut the power and you blundered around the sky for a bit before finally setting up to land on your field, that’d be okay. But you’d be chancing it. The forced approach is the most failed item on the flight test and a “failure to employ an organised approach” is the most common reason for failing it. It inevitably leads to you either under or overshooting the field.

The first method that is taught is the high/low key approach. This is meant to be easier for students to get a handle on, as you are effectively flying a circuit in order to land. Something that us students do a million times in the course of our training.

Basically you pick a field and trim for best glide. Then you pretend your field is the runway. You pick out a landmark that would be in the same place as your base turn and aim to get there at the same height as you would if you were in the circuit. This means that you alter your approach to that point depending on if you are high or low. Once you turn base it’s just like flying a standard landing. You can make last minute alterations by dropping flaps earlier or later or slipping it down if you need to.

The crux of it is, once you’ve picked your field you need to fairly quickly, mentally map an airport diagram around it. Identifying the downwind and base legs at the very least.

And it turns out that spatially challenged me has difficulties with that. Sometimes I can manage it but then I do something stupid like losing track of the field, or conversely I spend so much time keeping track of the field that everything else goes to pot.

If I make the field it is more by luck than judgement. Maybe a 50% success rate.

Not good, another approach is needed. Literally.

It turns out though, that there is another way, another option. One that Bob had mentioned at the very start but I had dismissed because technically the methodology is beyond the PPL and is more in line with the commercial flight test standards.

This one is a little bit more mathematical, but amazingly my mind seems to have latched on to the numbers and can make sense of them.

It relies on the magic “rate one turn”. A rate one turn basically takes 2 minutes to do 360 degrees. It is marked on your turn and bank or turn and slip indicator and is relatively easy to achieve and maintain. It is useful in instrument flying conditions as well but I’m getting away from the point.

The other thing you need to know about a rate one turn is that, when configured for best glide, you lose about  600 feet per minute in altitude. So in 360 degrees you will lose 1200ft.

Easy numbers and a surprisingly easy technique.

You pick a field (something I’ve finally managed to nail, now that I know what I’m looking for) and fly over it in the direction you want to land. You pick a point about a third of the way down and aim to be over that point at an altitude that is a multiple of 1200ft above ground level (so 2400ft, 3600ft etc.).
If you are too high then you fly past that point until you’ve lost half the extra altitude (you’ll lose the extra half on the way back).

Then it really is as simple as maintaining a rate one turn at 65 knots. Each multiple means one more turn. You basically spiral down.

Magically you find yourself on final approach to the field at exactly the right time and height.

It is a thing of beauty to behold.

Slight differences in terrain height mean that you have to finesse slightly on final, judicious use of flaps, slipping etc. But it works!

Two methods, two very different results.

I am so relieved to finally have found something that works for me consistently. I know that Bob went on an instructor’s course recently and there seems to be a big push towards teaching this method. It has many advantages, not the least being that you don’t lose sight of the field and are never flying away from it.  Despite the fact that it is viewed as a slightly more complex technique.


I’m glad Bob persuaded me to have another go at it, it really seems to work for me.

2 comments:

  1. Down here we are taught a variation of the high key low key approach. I won't go into detail because I don't want to confuse you. I might try the mathematical approach out myself at some point though!

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    1. I've got a solo flight coming up this week. I'll try to get one on film with some commentary. No promises though (about the voice over).

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