Steep Spirals

[EnRoute]

Just read over the "steep spirals" in my Airplane Flying Handbook. The one thing it mentioned about speed other than remaining constant in this altitude loosing maneuver is that "once the throttle is closed and gliding speed is established", am I too assume that this speed is that which provides for my best glide? Therefor although it is a steep altitude loosing maneuver, it is flown at a relatively slow airspeed?

Am I correct in assuming this?

 

[Clocks]

If I remember right there is no designated speed in the PTS.

 

[BrewMaster]

No speed in the PTS, but you would use your best glide.

 

[surreal1221]

No speed in the PTS, but you would use your best glide.

Correct.

We had our own standards during stage and EOC checks which was +/-5 kts of best glide.

Always enjoyed during steep spirals though.

 

[tgrayson]

am I too assume that this speed is that which provides for my best glide?

Not necessarily. Since you're not at max gross and you're pulling a load factor, sometimes close to 2, best glide is pretty much irrelevant. Plus, you're not trying to go anywhere, making it more irrelevant. Arguably, a speed closer to minimum power, which is less than best glide, would be more useful, because it would help you preserve altitude better in order to more easily complete three turns.

However, since you will be pulling close to 2 g's, you will experience an increase in stall speed of about 40 percent. If you add a comfortable margin over the stall speed, that's going to be in best glide territory, if not greater.

So you're free to pick a speed that works for you; the maneuver just requires that you keep it.

 

[Roger, Roger]

FWIW, the 172 works well at about 75 KIAS. The stall warning will be just barely whispering in the steep parts of the spiral.

 

[nosehair]

Not necessarily. Since you're not at max gross and you're pulling a load factor, sometimes close to 2, best glide is pretty much irrelevant. Plus, you're not trying to go anywhere, making it more irrelevant. Arguably, a speed closer to minimum power, which is less than best glide, would be more useful, because it would help you preserve altitude better in order to more easily complete three turns.

However, since you will be pulling close to 2 g's, you will experience an increase in stall speed of about 40 percent. If you add a comfortable margin over the stall speed, that's going to be in best glide territory, if not greater.

So you're free to pick a speed that works for you; the maneuver just requires that you keep it.

That right there is about the best esplanation I've ever heard about the speed during this maneuver. It explains the concept and reason for minimum sink, and a reason to have a margin above that speed when advisable.

The whole PTS TASK includes, in the beginning, "Demonstrates knowledge of the elements related to Steep Spirals."

This little gem does an excellent job of covering that part.

 

[mattp1803]

I think what might be mixing you up is the word "steep". In this particular maneuver you pick a point and try to keep your wheel on it, turning 360 degrees around it. You are making steep banks at times, especially when turning into the wind. You will maintain best glide, so whatever it takes to keep your speed.

 

[Hubbs]

I think what might be mixing you up is the word "steep". In this particular maneuver you pick a point and try to keep your wheel on it, turning 360 degrees around it. You are making steep banks at times, especially when turning into the wind. You will maintain best glide, so whatever it takes to keep your speed.

The purpose of the maneuver is to maintain a constant radius about your point, much like turns about a point, but descending. The smaller the radius (the closer to the point) the steeper the bank required, and the greater the descent rate for a given airspeed. You don't need to 'keep your wheel on it' you just need to maintain a constant radius, you can select whatever radius you choose.

You angle of bank required is dependent on your ground speed, the faster you are the more bank required, so your steepest bank is actually gonna be downwind.

I don't really understand what you mean by "You will maintain best glide, so whatever it takes to keep your speed". As you vary your bank you will need to adjust your pitch accordingly to maintain your airspeed.

 

[itsbfinch]

I have had a few arguments about steep spirals in the past. When I first learned them I did them at 90kts in a C-182 gear up flaps up. The theory was that since you are circling over a selected emergency landing area there was no need to keep best glide speed since you are right above it which made sense to me. When I did my CFI training my instructor had me do them with full flaps, gear down, at VFE, needless to say your sink rate was pretty fast. Her theory was your doing a steep spiral to loose altitude as fast as possible, maybe for depressurization or some passenger sickness. I really didn't like her theory behind it becasue I thought that dealt more with emergency descents. I have also been told to do them at best glide, the problem there is that your turns are not really that steep in some airplanes, which the examiner did not seem to like. So by FAA standards you can do any speed you would like as long as you hold that speed. But in reality I would choose something a little faster, depending on what plane, especially since you will be pulling a couple g's and increasing your stall speed.

 

[jrh]

I know I'm jumping in to this discussion kind of late, but I wanted to point out that there really is no practical use for the steep spiral. It's simply a maneuver to demonstrate mastery of the aircraft, same as chandelles or lazy eights. I would advise students of this rather than make up a weak reason for why the maneuver might be used in flight as a commercial pilot.

In the real world, I can't think of any reason to do a steep spiral. I've spiraled down through holes in clouds and just "made it work" regardless of speed or ground track. Stay in the hole and go down, it's as simple as that.

I've also had an engine failure while descending after dropping off a load of skydivers and the steep spiral was the last thing on my mind--I did like I always do, which is maneuver to glide in to the pattern and land.

When dealing with sick passengers, descending quickly in a spiraling motion is a relatively surefire way to get puked on.

Pick a speed, pick a radius, hold them constant, and you just did the maneuver correctly. Anything beyond that is getting overcomplicated, in my opinion.

 

[JulietBravo]

Pick a speed, pick a radius, hold them constant, and you just did the maneuver correctly. Anything beyond that is getting overcomplicated, in my opinion.

:yeahthat: During my commercial, I learned from one instructor to maintain best glide and get 3 turns around. I then was told by another instructor that you don't have to do that, we cranked it over to about 50-60 degrees of bank and maintained 80kts and got 3 turns around pretty quick. Doesn't matter how you do, just do it.