Flat Turns
 

We've got a maneuver in the Army called a flat turn and I'm wondering if anyone else in the flying world has cause to do them.

The goal is to turn 360 degrees in 12 minutes with out exceeding a 3 degree bank or 5 degree pitch.

Never done it in the T-37/T-1/C-17, never even heard of it. Sounds interesting, I think I may try it on my next local training sortie for kicks.

Physics
 

Simple physics:

a=v(squared)/r

a=acceleration
v=velocity
r=turn radius

"a" is the acceleration in the horizontal that "accelerates" your velocity vector in a new direction, resulting usually from banking an airplane, and "borrowing" a component of said lift to use in the horizontal--a banked turn.

If you hold the rudder to floor and maintain no-bank, you're in a sideslip--and EVERY airplane will turn. This is because the sideslip is an angle of attack--against the side of your fuselage, so it generates horizontal lift. Not very effectively, but it does. But:

The slower you are, for the miniscule amount of "a" you generate in sideslip, the smaller your turn radius--and the quicker you turn. (another formula for Theta-dot that I haven't memorized).

So, in a fixed-wing 60-kt airplane, you can do a no-bank turn in 12 minutes. At 480 kts, it would take about 2-3 hours.

And, a hovering helicopter can do it in less than a minute (I would think!).

I'm guessing you do them in the RC-12 so you can keep an antenna pointed at a specific area of interest (and not mask it) while still maneuvering the airplane.

You could also do them by splitting the throttles (still creates yaw).

UAL T38,

You've got the physics down (we use the rudder method because we can only have a 200 lb fuel imbalance).

The real question I've got is, does any one else have a reason to do them other than just for the heck of it.

Maybe to avoid showing too much profile to another aircraft at the same altitude? I dunno.. :D

I guess it depends on the diameter of the antenna - the E6B guys would fly around at very steep bank angles dragging miles of antenna!

In reference to the E-6B wire: The steep angles you refer to actually cause the miles of antenna to be mostly vertical which results in better signal transmission. The wire actually does fly (create lift) and needs to be stalled to hang down vertically, thus the plane flies in a relatively tight circle (30-50 AOB), around stall + 10% to achieve this "verticality."

OBTW...the antenna's diameter is no thicker than your pinky fingure.

this is interesting, this pinky size antenna ya'll speak of. Please elaborate, what would the techincal name be of such a contraption?

Great explanation, thanks! I was referring to the diameter of the loop that the cable made not the actual cable. Would it fair to say that frequency propagation is directly proportional to the loop diameter? If you need an ULF signal you need a big loop?

Very-Low Frequency
 

VLF--a frequency so low, the waves will actually propagate through earth---and water. The Navy uses it to communicate with subs, for National Command and Control of nuclear subs and ICBMs. The wavelength is something measured in miles (2-4; can't remember).

The wire is as fat as your pinky because it is about 2 miles long!! (So it needs to be that thick to support the weight of 2 miles of cable). I believe it is weighted-down with about a 50lb weight on the end, so, as the E-6B (TACAMO) circles overhead, making the weight almost stationary, the antenna wire scribes a cone above it--remaining almost vertical.

I'm pretty sure each antenna is used one time, then snipped-off--too hard to reel back in.

DTWA, STWA, UTWA.....take your pick!

http://en.wikipedia.org/wiki/TACAMO


http://www.fas.org/nuke/guide/usa/c3i/vlf.htm

It gets reeled in most of the time. Takes 10-15 minutes. sometime it falls off due to icing, sometime it gets tangled (picture a fouled up fishing reel) and has to be snipped.

The E-2 guys do those type of turns. Helps steady the radar picture when flying with the Airwing around the ship.