The Inside Loop

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The Inside Loop

Post by Greg Russell-Brown on Mon Nov 21, 2016 8:38 am

Although being a fairly basic manoeuvre the inside loop has a certain mystique associated with it and it is also one of the (building blocks) or foundations for more complex manoeuvres such as the Immelmann Turn (so named after the German pilot Max Immelmann who invented the manoeuvre in World War 1).

The Cuban Eight and two loops with half rolls are other examples of the inside loop combined with other manoeuvres which we shall discuss in detail at another time.

As always ensure you begin with sufficient height to recover in case of disorientation - (three mistakes high is a good rule of thumb!)

We will first practice this manoeuvre heading into wind and it is typically executed in the centre of the (aerobatic box) i.e.: directly in front of the pilot and approximately 50 Metres away in the direction you are looking - (you should be standing with shoulders aligned with the runway in use, in other words looking across the width of the runway and not down the length).

To begin we start from upright level flight and set throttle to 100% approximately 50 metres before the aircraft arrives at the centre of the box (once again which is in front of you) and ensure you are approaching from downwind, the application of full power allows the aircraft to accelerate to its maximum level flight speed prior to manoeuvre execution and approaching from downwind obviously will result in the manoeuvre being done into wind which is easier when first learning this manoeuvre to begin with.

Precisely at the centre of the box gently apply a few degrees of up elevator and the aircraft will commence the loop, (ensure the wings are kept as level as possible throughout the entire manouvre, if they are not level you will wind up performing a looping corkscrew rather than a perfect inside loop).

As we approach almost the halfway point of the loop (at around 160 degrees of attitude change ie: just before the aircraft is inverted at the top of the loop) start releasing the elevator slightly but not completely and also reduce power to around 20% over approximately 3 seconds.

By this time the aircraft will now be at approximately 200-220 degrees of attitude change and will have gone past the inverted stage at the top of the loop - (a full inside loop is of course 360 degrees of attitude change to resume upright level flight in the same direction of the initial entry).

At this point when we start heading towards terra firma and as a result thereof gravity although of course always being constant starts exerting more (apparent) force on the moving aircraft because we are no longer flying in an arc overhead but falling back to earth so to speak so we have to overcome that force plus the kinetic energy from the angular change, as a result a little more up elevator is needed than that used in the initial pull up at the start of the manoeuvre in order to keep the loop geometrically correct i.e.: perfectly circular and we have already reduced power to maintain the same flight speed throughout the manoeuvre - full power on the climb and reduced power during the dive portions of the loop.

Note: a higher speed whilst changing heading or direction in any manoeuvre also increases the G forces the aircraft is subjected to if it is to exit at the desired point:

"G" force or gees are the result of kinetic energy versus angular change in any moving object.

Physics dictate that kinetic energy will keep an object travelling through space on the same trajectory without outside influence, if this trajectory is changed then acceleration forces are caused-we call them G forces: 1 G =
1 gravity or for example your normal weight at sea level.

In the case of a miniature/model aircraft that weighs say 5 Kg, when doing a standard inside loop you could expect approximately 3 gees of acceleration force on the airframe thus the aircraft would actually weigh 15 Kg during the manoeuvre!

Once the aircraft has completed a full 360 degrees of attitude change the inside loop is complete and the aircraft should be at exactly the same point where you first started the manoeuvre, release the up elevator input and then restore power to cruise setting (approximately 75%) and resume normal upright level flight.


The purpose of learning these manoeuvres is primarily to have Fun with a capital F!

However should one wish to attain great scores in aerobatic competition this is what the judges will be looking for:
1: A perfectly circular loop placed right in front of them in the dead centre of the box
2: Exactly the same flight speed throughout the manoeuvre
3: Wings dead level throughout the manoeuvre
4: No drift away from or toward the pilot during the loop caused by wind or incorrect aircraft tracking/heading - (rudder may be carefully used to compensate for any drift)
5: Entry and exit points of the manoeuvre in the exact same physical space

Downwind inside loop:
Executing this manoeuvre is pretty much the same as mentioned above for the into wind inside loop but the main difference you will find is more up elevator is needed when starting the initial pull-up as there is less airflow over the aircraft (flying at the same relative groundspeed as the into wind loop), and less elevator is required during the top of the loop as the aircraft then is heading into wind and must penetrate further upwind to keep the loop uniform.

Advanced:
In the MAAA Gold wings schedule one of the manoeuvres specified is three inside loops done from both directions.
i.e.: one set of three loops from left to right and one set from right to left.

These three inside loops are superimposed on each other, in other words they are all done in the same physical space so if one was to draw a picture of the manoeuvre it would look like just one loop.

The main difficulty in executing three loops superimposed on each other is to avoid having the loop set drift downwind and thus the loops would not be in the same position.

This drift is best corrected by careful use of elevator and power and thus allowing the aircraft to start subsequent loops at the same initial starting position.
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Greg Russell-Brown
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