Steep Spiral

minds_warped

New Member
Can someone tell me what is required for the steep spiral maneuver? I'm doing my CFI single add on and cannot remember if flaps are required, or what airspeed. The PFH and PTS does not say, nor do any of my other books. I want to say no flaps and best glide speed no more than 60 degree bank, but that does not give the greatest rate of descent. What does the examiner want to see? Thanks
 

pilot602

If specified, this will replace the title that
It's not about greatest rate of descent (that's an emergency descent). I've been using best glide and no steeper than 30º of bank.

In the emergency descent (where you spiral) it's full flaps and keep it pegged at the top of the white arc and 30º - 50º of bank. It'll give you a nice 1500 fpm in a 172 with little trouble.
 

ready2fly

Well-Known Member
We've been using the best glide speed too, but we keep the bank between 30 degrees and 45 or so.

From your altitude, (if I understand it correctly), you have to complete three full turns down to TPA above your "landing" point.
 

Alchemy

Partner, Ally, Friend
I've always done steep spirals with 45 degrees of bank at the shallowest and 60 degrees of bank at the steepest point. Power is at idle, carb heat on, and pitching for best glide at max gross weight + 5 knots. The PTS says not to exceed 60 degrees of bank, but doesn't specify a minimum bank angle. Remember that it is a STEEP spiral, I take this to mean they want to see some pretty steep bank angles. The danger is of course that the stall speed increases as you steepen your bank angle. Make sure you can stay at least 10 knots above stalling speed at your steepest bank angle with the airspeed you select to maintaint for the maneuver. Also you must be very careful not to exceed 60 degrees of bank, as that is a violation of the FAR's unless you're strapping a parachute.

The PTS is pretty vauge on this maneuver, so there should be some flexiblity in what the examiner will accept as a steep spiral. As long as you adhere to the 6 critera spelled out in the PTS, you should be fine.
 

MidlifeFlyer

Well-Known Member
He wants to see the maneuver that's described in the FAA's Airplane Flying Handbook:

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Steep Spiral

A steep spiral is nothing more than a constant gliding turn, during which a constant radius around a point on the ground is maintained similar to the maneuver, turns around a point. The radius should be such that the steepest bank will not exceed 60°. The objective of the maneuver is to improve pilot techniques for power-off turns, wind drift control, planning, orientation, and division of attention. This spiral is not only a valuable flight training maneuver, but it has practical application in providing a procedure for dissipating altitude while remaining over a selected spot in preparation for landing, especially for emergency forced landings.

Sufficient altitude must be obtained before starting this maneuver so that the spiral may be continued through a series of at least three 360° turns. [Figure 6-15] The maneuver should not be continued below 1,000 feet above the surface unless performing an emergency landing in conjunction with the spiral.

Operating the engine at idle speed for a prolonged period during the glide may result in excessive engine cooling or spark plug fouling. The engine should be cleared periodically by briefly advancing the throttle to normal cruise power, while adjusting the pitch attitude to maintain a constant airspeed. Preferably, this should be done while headed into the wind to minimize any variation in groundspeed and radius of turn.

[Figure 6-15.—Steep spiral.]


After the throttle is closed and gliding speed is established, a gliding spiral should be started and a turn of constant radius maintained around the selected spot on the ground. This will require correction for wind drift by steepening the bank on downwind headings and shallowing the bank on upwind headings, just as in the maneuver turns around a point. During the descending spiral, the pilot must judge the direction and speed of the wind at different altitudes and make appropriate changes in the angle of bank to maintain a uniform radius.

A constant airspeed should also be maintained throughout the maneuver. Failure to hold the airspeed constant will cause the radius of turn and necessary angle of bank to vary excessively. On the downwind side of the maneuver, the steeper the bank angle the lower the pitch attitude must be to maintain a given airspeed. Conversely, on the upwind side, as the bank angle becomes shallower, the pitch attitude must be raised to maintain the proper airspeed. This is necessary because the airspeed tends to change as the bank is changed from shallow to steep to shallow.

During practice of the maneuver, the pilot should execute three turns and roll out toward a definite object or on a specific heading. During the rollout, smoothness is essential, and the use of controls must be so coordinated that no increase or decrease of speed results when the straight glide is resumed.
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EDUC8-or

Well-Known Member
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Remember that it is a STEEP spiral, I take this to mean they want to see some pretty steep bank angles

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I totally agree. Our chief pilot and most of the DE's around here agree that you should immediately roll into a steep bank after you're over your point. If you're only using 30 degrees of bank and you're at 5000' you could be pretty far from your point.

One good hint I learned: Pick 2 roads/powerlines/etc... that cross and pick the point where they cross as your point. From the right seat, you're not going to see your point. (If you can, you're not using enough bank) As you are parallel to the first road you should roll into your steepest bank just as you cross the other road. Pick 4 spots on those roads that are equidistant from your point. Then just make sure you keep flying over the same spots on the roads and you should be right over your point for the entire maneuver.
 

ready2fly

Well-Known Member
EDUC8-or: you're right. After I read the responses, I started thinking that 45 degrees wasn't quite right, so I called my instructor and turns out - I misspoke. It is a bank angle UP TO, but NO MORE THAN 60 degrees of bank. Whatever works to keep you over your point and will get you down to TPA w/in three full turns.
 

Icelandair

New Member
We do them here in North Dakota at 95 knots in the Arrow, our stall speed is 60 clean. We do them with flaps up, gear up too.
 

cime_sp

Well-Known Member
FSI always did them at best glide + 10 knots. This allowed a safety margin because of the increased stall speed from the higher load factor. We also did up to a 60 degree bank. The steeper you do them the easier they become. They are over quicker and with much less drifting the steeper you go. Also you can get more turns in for your loss of altitude.
 

MidlifeFlyer

Well-Known Member
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FSI always did them at best glide + 10 knots. This allowed a safety margin because of the increased stall speed from the higher load factor.

[/ QUOTE ]What higher load factor? Remember the steep turn here is in a gliding descent.
 

SteveC

Really?
Staff member
[ QUOTE ]
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FSI always did them at best glide + 10 knots. This allowed a safety margin because of the increased stall speed from the higher load factor.

[/ QUOTE ]What higher load factor? Remember the steep turn here is in a gliding descent.

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Funny that a lot of people miss that one. I've heard more than one person talk about increased stall speed in a bank, without stipulating that it is in level flight. It's angle of attack, not bank (alone), that influences stall speed.
 

Alchemy

Partner, Ally, Friend
Good point about the stall speed not increasing since you're descending, I didn't think about that. So by all means, use 45-60 degrees of bank.
 

E_Dawg

Moderator
I know what you guys are saying about the stall speed not increasing, for example in the Lazy 8 you're at 30 bank but the nose just slices through the horizon, you're not pulling any more Gs than normal (you're accelerating downwards).

But in a steady state descent you're not accelerating toward the ground (VSI needle is not moving), so when you increase bank you are pulling Gs and increasing the stall speed. It's just like doing them in level flight, except that now weight is 'thrust' instead of the engine.
 

MikeD

Administrator
Staff member
Reader's Digest version: Just don't exceed critical AOA at any bank angle/airspeed, combo thereof, and you're fine.
 

pilot602

If specified, this will replace the title that
[ QUOTE ]
[ QUOTE ]
FSI always did them at best glide + 10 knots. This allowed a safety margin because of the increased stall speed from the higher load factor.

[/ QUOTE ]What higher load factor? Remember the steep turn here is in a gliding descent.

[/ QUOTE ]

But where's the lift vector pointing? More bank = higher stall speed. In this case it may be a very slight increase but it will increase. "Load factor" isn't the only thing that affects the stall speed.

As to the steepness of the turns ... this is not an emergency descent. If anything it's an excercise in accuracy (the ability to remain over a fixed point on the gorund and lose altitude at the same time). Your rate of descent is not important.

However in a spiraling, emergency descent the rate of descent is important and that's when you pop the gear, flaps, anything you've got, roll it into a nice bank and keep it pegged on the high side of the white arc. The aircraft will drop like a rock with a relatively slow airspeed (whatever the top of the arc happens to be).

The two are different and I think a lot of people "blend" the two.
 

MidlifeFlyer

Well-Known Member
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"Load factor" isn't the only thing that affects the stall speed.

[/ QUOTE ]It's not? I thought that level flight stall speed increased in a bank =because of= increased load factor.
 

cime_sp

Well-Known Member
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[ QUOTE ]
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FSI always did them at best glide + 10 knots. This allowed a safety margin because of the increased stall speed from the higher load factor.

[/ QUOTE ]What higher load factor? Remember the steep turn here is in a gliding descent.

[/ QUOTE ]

Do a 60 degree gliding turn....tell me where the stall horn starts to go off. I can guarantee you that it is higher than "normal" stall speed. Even though you are descending you are getting closer to the critical angle of attack.
 

pilot602

If specified, this will replace the title that
[ QUOTE ]
[ QUOTE ]
"Load factor" isn't the only thing that affects the stall speed.

[/ QUOTE ]It's not? I thought that level flight stall speed increased in a bank =because of= increased load factor.

[/ QUOTE ]

But where's the lift vector pointing?
 

MikeD

Administrator
Staff member
I reiterate...
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Reader's Digest version: Just don't exceed critical AOA at any bank angle/airspeed, combo thereof, and you're fine.


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raises/lowers stall speed is moot, in the sense that it's the only stall-related speed to worry about, since you can stall at any speed/configuration/bank angle, etc, et al. CAOA is key.
 

E_Dawg

Moderator
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
"Load factor" isn't the only thing that affects the stall speed.

[/ QUOTE ]It's not? I thought that level flight stall speed increased in a bank =because of= increased load factor.

[/ QUOTE ]

But where's the lift vector pointing?

[/ QUOTE ]

Why's it matter where it's pointing?? Like MikeD said all that matters is how close you are to CAOA. The lift vector could be pointing towards the earth (like it is during the inverted portion of a 1G roll), you still won't stall. Same idea; you can fly much lower than Vs and not stall, you just have to be doing a push over and flying at less than 1G.
 
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