spinning

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lanceair
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spinning

Post by lanceair » Sat Jan 02, 2010 9:22 am

Hi all,
I've been instructing on a Cessna 172/P and whenever I demonstrate a spin it goes into a spiral dive. I enter it just before stall, I don't release the back pressure on the control column (fully aft), I have it trimmed for best glide (65 KIAS), full rudder is held in, and the a/c is in utility category. Just wondering if anyone has some insight into why it doesn't remain at stall?
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Tango01
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Re: spinning

Post by Tango01 » Sat Jan 02, 2010 9:43 am

Make sure you stall it first. I used to spin the C172R with 1800 rpm at least. Get that rudder in fully and hold it. It doesn't like to spin.
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5x5
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Re: spinning

Post by 5x5 » Sat Jan 02, 2010 9:57 am

Not sure of the P model, but I agree with Tango1 to make sure you have power on at stall/spin entry - in the Ms I'm familiar with about 2,000 rpm is good. Also, spinning to the left works better than to the right (the natural yaw to left when power is on makes it easier). Reduce power to idle as the nose descends through the horizon.

Do you get the opportunity to go flying by yourself and practice? Or better yet, go for a flight with your CFI and make sure you can do it well before demoing to a student. An added benefit is that your CFI will likely take the time to show some other tricks of the trade as part of your ongoing development training.

It's tough to try and show something to a student when you aren't totally confident it's going to work. And you can't try it over and over with a student along - you need time on your own to get it nailed.
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lanceair
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Re: spinning

Post by lanceair » Sat Jan 02, 2010 10:15 am

When i was doing my training, i was always taught to do a power off stall then spin it from there. How would power-on entry prevent the a/c from entering a spiral?
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cgzro
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Re: spinning

Post by cgzro » Sat Jan 02, 2010 10:39 am

Suggest you approach it more aggressively. Pull the yoke back very crisply, you want to see the nose come up 5-10 degrees and then be equally agressive with the rudder .. and don't relax the backpressure or use any aileron (make sure they are neutral and keep them there).
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Re: spinning

Post by ETOPS » Sat Jan 02, 2010 11:21 am

lanceair wrote:How would power-on entry prevent the a/c from entering a spiral?
Its a question of rudder authority. It doesn't have enough, and power is required to assist with this. I remember having to use 1500RPM in one particular 172 for a second or two while "kicking" the rudder. It seemed to do the trick.
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Big Pistons Forever
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Re: spinning

Post by Big Pistons Forever » Sat Jan 02, 2010 11:44 am

The C172 is so reluctant to spin that it makes it impossible to demonstrate any kind of realistic spin scenarios. Therefore it is important that the PGI emphasize that virtually all other airplanes are not as forgiving and to concentrate on the importance of recognizing and immediately correcting uncommanded Yaw particularly in the slow flight regime. With respect to getting a clean spin entry you need to get the aircrafts inertia moving in a prospin direction (ie increasing yaw and increasing angle of attack)
before the stall. As mentioned above start with 1800 RPM and plan a left hand entry, then as aircraft is deaccelerating through around 50 knots a full and rapid rudder application first to start the yaw followed by a brisk application of full back stick and then reducing the power to idle as the spin is established. The usual problem with the airplane refusing to enter the spin is too timid application of the controls.

It should be noted that in the C172 the most dangerous part of this manoever is the difficulty of maintaining the spin even with full into spin controls. It is very easy for the spin to transition into a spiral dive and any delay in recovery will result in excessive airspeed. Therefore it is vital that the airspeed is monitored throughout the manoever and the spiral dive recovery be intiated at the first sign of increasing airspeed.

But at the end of the day it is not important that you can get into a spin the important thing is early recognition of an impending spin and the proper action to avoid one.
This must start with the importance of controlling yaw during the inital stalling lessons. The airplane cannot spin if it is not yawing even if it is in the fully stalled state.
Finally I am a great believer in starting all my PGI's with a discusion about the PDM relavant to the exercise. The accident record shows most spin accidents occur close to the ground and therefore below an altitude where recovery is possible. Therefore it is very important to review scenarios where mistakes at low altitudes which can lead to a risk of reparting from controlled flight are well understood ( ie the the skidding base to final turn and illusions created by drift)
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MichaelP
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Re: spinning

Post by MichaelP » Sat Jan 02, 2010 11:49 am

Aha, Big Pistons has stated it.
This is what I just wrote:

The Cessna 172 of any model does not spin when in the utility category.

If you try to spin it in accordance with the POH it will spiral every time.

Adding lots of power and dynamically stalling the aircraft with pro spin inputs is not approved in the POH, but at least you'll get half a turn out of it before you spiral.
Leave power on and she'll stay in a spin to the left.

It's not worth the bother. Many many people have this frustration.
For the CPL flight test you'll have to fudge it like everyone else does.
If you're a short pilot you'll have a lot more trouble than a long legged one.

Find a Tomahawk, a Citabria, or a Diamond DA20, spin it by approaching the stall power off and dynamically stalling the aeroplane five knots above the normal stall speed with pro spin inputs and then check the ASI while in the true spin. It should be low and perhaps oscillate up and down a little.

The Cessna 172 is actually a good spinning aeroplane as some accidents to fully loaded aircraft will attest, so be careful.
Be prepared for the fully loaded Cessna 172 by spinning something that really does spin.

This is the most horrific video I've seen in a long while:

http://www.youtube.com/watch?v=DFWMBT1zDlI
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Tango01
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Re: spinning

Post by Tango01 » Sat Jan 02, 2010 11:59 am

That's a horrible video Michael. Goes to show, that turning back after an EFATO at low altitude is not a good idea. Def good video to show students (Intensity)
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Re: spinning

Post by Big Pistons Forever » Sat Jan 02, 2010 12:00 pm

The C 150 will do a proper spin and therefore is a far better airplane to teach this exercise in. The best way to learn about spins is as part of an aerobatics course. I highly recommend aerobatics training for everyone doing flight instruction. Finally treat the spin with respect and if the airplane does anything weird recover immediately. This is especially important if the aircraft has an unusually nse high attitude in the entry or the nose starts rising after the spin is established. I recommend that instructors who have not had aerobatic training do not exceed 2 turns when spinning.
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AuxBatOn
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Re: spinning

Post by AuxBatOn » Sat Jan 02, 2010 12:02 pm

Tango01 wrote:That's a horrible video Michael. Goes to show, that turning back after an EFATO at low altitude is not a good idea. Def good video to show students (Intensity)

I can be a good idea. You just need to know what kind of energy state (altitude and airspeed) you need in order to make it back, taking into consideration the wind.
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Big Pistons Forever
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Re: spinning

Post by Big Pistons Forever » Sat Jan 02, 2010 12:13 pm

A terrible video but a hugely important teaching aid. The take away is to concentrate on the seconds after the engine starts to sputter. The nose is only lowered slightly and then the turn back is started, he gets part way around and then boom stall spin. It is vital to aggressively lower the nose at the first sign of power loss. A good exercise is to set up in the practice area at a safe altitude. a full power trimmed climb at Vx. When the aircraft is stable, smoothly but quickly retard the throttle to idle and note how quickly the airspeed decays. It will make a big impression on the student. I also make the (PPL student) pilot declare he/she will not turn back below 1000ft AGL as part of their pretakeoff brief.
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Tango01
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Re: spinning

Post by Tango01 » Sat Jan 02, 2010 12:25 pm

AuxBatOn wrote:
Tango01 wrote:That's a horrible video Michael. Goes to show, that turning back after an EFATO at low altitude is not a good idea. Def good video to show students (Intensity)

I can be a good idea. You just need to know what kind of energy state (altitude and airspeed) you need in order to make it back, taking into consideration the wind.

While that's true, the so called "Impossible Turn" can be made possible, but you need quick reaction, assuming the power loss occurs at Vy, perfectly coordinated 45 degree banked turn at something like 5% above your stall speed through something like 190-220 degrees in a teardrop flight path (IIRC). Wind, altitude, reaction time, aircraft type, pilot experience, blah blah too many variables to mention. Im not arguing with you Aux, because you are right, however, do you think that's something you should be teaching to your students? How many PPL students are even taught proper T/O Briefings?
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MichaelP
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Re: spinning

Post by MichaelP » Sat Jan 02, 2010 12:37 pm

Turning back from the situation in the video was impossible.
It's possible in many little aeroplanes from a steep descending turn from above 400 feet. But only for a skilled quick reacting pilot.
Tests show that 60 degrees of bank while allowing the aeroplane to drop will lose you less height than a coordinated turn but we shouldn't teach it that way. This sort of thing is for skilled pilots.

Look at the rudder input just prior to the spin entry.

The girl on the wing is probably equivalent to up elevator!

A Tiger Moth will not spin if you apply in-spin aileron during entry or are too slow getting the stick back.
Many 'spin' accidents are in fact spirals, but the video shows true spin entry, very sad because it's apparent from the overhead shot that there's a lot of clear ground beyond the crash site.

A similar incident took place at Shoreham and the Tiger nosed over after touch down.
The girl on the wing undid her straps as the aeroplane crashed and rolled a little winded away from it.

Another one was when Barry Tempest had his daughter on the wing, hit a wire and flopped over into a river.
The two of them swam around the wreckage looking for each other. Always agree to swim in different directions!

We do a pre takeoff brief, "If the engine fails on the runway close throttle stop straight ahead.... "lower the nose and land on the remaining runway"... "Lower the nose, 60 knots and pick a place within 45 degrees of the nose"... This is to prime the mind not to do the rabbit brain thing and turn back!

After all this I seemed to be lined up with a CPL preflight test in a Cessna 172 today... I'll have to go through this spinning the C172 sham!
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Re: spinning

Post by AuxBatOn » Sat Jan 02, 2010 12:52 pm

Tango01 wrote: do you think that's something you should be teaching to your students?
Past the PPL, sure. It teaches the student to fly the airplane in its whole envelope and gives him 1 more thing that he can use in case shit hit the fan.

Here's a good example on a succesful one:

http://www.youtube.com/watch?v=mqmYxgZ7Mm8
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Tango01
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Re: spinning

Post by Tango01 » Sat Jan 02, 2010 1:00 pm

http://www.maxtrescott.com/max_trescott ... 763e5b970b

"What's even sadder than having a pilot die while trying the impossible turn is having a CFI and a client die while practicing the impossible turn at low altitude. I’ve haven’t researched how often this happens, yet I’m aware of one fatal crash and one non-fatal crash that destroyed an airplane, both of which happened within the last couple of years here in California. In both cases, the aircraft took off from an airport, the power was pulled off to simulate an engine failure and the airplane was turned back to the runway. While I didn’t know the occupants of the fatal crash, I do know the CFI who survived the non-fatal crash."
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Re: spinning

Post by AuxBatOn » Sat Jan 02, 2010 1:05 pm

Tango01 wrote:http://www.maxtrescott.com/max_trescott ... 763e5b970b

"What's even sadder than having a pilot die while trying the impossible turn is having a CFI and a client die while practicing the impossible turn at low altitude. I’ve haven’t researched how often this happens, yet I’m aware of one fatal crash and one non-fatal crash that destroyed an airplane, both of which happened within the last couple of years here in California. In both cases, the aircraft took off from an airport, the power was pulled off to simulate an engine failure and the airplane was turned back to the runway. While I didn’t know the occupants of the fatal crash, I do know the CFI who survived the non-fatal crash."
It comes down to know in which energy state you can make the turn back. It's better to know and not attempt unless you have the required energy than not knowing and not making it.

How you figure that altitude/airspeed combination? By trying it with a good engine. That's why I think this manoever should be taught by instructor and understood by all, post-PPL.
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MichaelP
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Re: spinning

Post by MichaelP » Sat Jan 02, 2010 1:08 pm

With all due respect Aux Bat the video is from a jet trainer with a very low drag coefficient (BAe explained to a US General that they didn't have enough budget to design in the drag!).

A friend of mine did the same thing in an Airbus 340 with four flame outs going out of Kai Tak... in the simulator!

But there's a world of difference in a low and slow draggy light aircraft.
It is always better to lower the nose, ensure you have the speed, and then see how much height you have to play with (QFE).
Since most flights turn crosswind at 500 feet or so it is practical on a low wind day to turn back to the runway from this point if the 90 degree turn has already been made.
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Tango01
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Re: spinning

Post by Tango01 » Sat Jan 02, 2010 1:12 pm

Fair enough, but I hope you practice this at a safe altitude. I don't think the value gained from this exercise warrants the high risk involved in performing it al low altitude.
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Re: spinning

Post by AuxBatOn » Sat Jan 02, 2010 1:27 pm

MichaelP wrote:With all due respect Aux Bat the video is from a jet trainer with a very low drag coefficient (BAe explained to a US General that they didn't have enough budget to design in the drag!).
I understand, it was the only video that I knew of.
MichaelP wrote: But there's a world of difference in a low and slow draggy light aircraft.
It is always better to lower the nose, ensure you have the speed, and then see how much height you have to play with (QFE).
There is no point going faster than best glide, unless you want to kill energy. If you make that turn at best glide, you will have a reasonable turn radius and have a better chance of making it. If you have parralel runways, even better. Way back, I found that I could do it in a C-150 from 350' on the same runway and 300' on a parralel runway IIRC.
MichaelP wrote: Since most flights turn crosswind at 500 feet or so it is practical on a low wind day to turn back to the runway from this point if the 90 degree turn has already been made.
We will agree that post-flight training, the aim is not to practice touch&go anymore, but to go from A to B, in which case, you will exit the circuit, whether it's straight ahead or turning in whatever direction. I think it's important to know all your options and be able to execute them. In my mind, a turn back is just as valid as landing in a field. In fact, if I can make it, I'd rather land on a piece of concrete than a field.

Tango: I always took someone with me that would keep an eye on the speed. I did it from a quiet airport. I did do it from the real scenario: 400' after take off. If it becomes obvious that you can't make it (ie: field goes up in you FOV), then I'd level the wings and go full power right away. Before that, you're right, I'd practice from a higher altitude, and see what combination of bank angle/nose down attitude would give me the best performance and how much altitude I needed.
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Tango01
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Re: spinning

Post by Tango01 » Sat Jan 02, 2010 1:37 pm

Aux, I do understand now how you went about it. Good call to have somebody monitoring your flying. You obviously have a lot more experience than me, its just something I wouldn't do at this stage unless I went up with somebody and/or practiced at a safe height.

To your defence from what Michael was saying, here is a textbook example:


Return to runway after simulated engine failure at 800'AGL. Flaps, slip, and slight s-turns were utilized to minimize chance of overrun.

Aircraft is a late 1970s C172, 160 HP. Climb performed at Vy; 6 second delay after engine failure and before turn started; turn airspeed is 75kts. Density altitude is around 1000' and headwind is about 15 kts.


http://www.youtube.com/watch?v=SNgoOFq87aY
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Tango01
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Re: spinning

Post by Tango01 » Sat Jan 02, 2010 1:51 pm

One more thing. This topic started as a spin entry question. To help out the OP, he/she is asking how to spin the C172P. I hope this video gives you an idea. Read what 5x5 and BPF said also.

http://www.youtube.com/watch?v=sxBQBEMyuUw


Gotta love youtube!
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Re: spinning

Post by ry6198 » Sat Jan 02, 2010 8:12 pm

Hey Lance what i always did was when you are going to spin to the left is to have a bit of right rudder on then just before the stall kick full left rudder and give a little shot of power, and then as soon as the a/c starts to drop its wing i pull the power to idle. just what i did to get the 172 going into a good spin and it worked for me
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Re: spinning

Post by AEROBAT » Sat Jan 02, 2010 9:33 pm

I have never seen a 172 stay in a true spin once you relax the control inputs. Flying in the utility C of G I think they won't stay in a spin. I never have flown a P model the newest was an M with LR tanks I used to own. I found I had to almost snap it into a spin, that being fairly abrupt use of the controls and a dash of power. Even then it would stop the rotation after a couple of turns when you relaxed the input, power at idle of course.

The 150 will stay in a spin however.
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Old Dog Flying
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Re: spinning

Post by Old Dog Flying » Sat Jan 02, 2010 10:11 pm

"The Cessna 172 of any model does not spin when in the utility category.

If you try to spin it in accordance with the POH it will spiral every time."

Pretty broad statement but then again our resident expert from Dear Old Blighty probably has never spun an older model C172...and yes Michael they do spin power off without developing into a spiral...but then again they were not designed and built in Britain.

Only the second day of 2010 and his nibs is at it again, slamming anything and everything on the left side of the "Pond"
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