How to avoid flying behind the power curve.

[t-bird]

Flying behind the power curve is probably the most common reason for gyro accidents.

The reasons for these accidents are usually

- Down drafts
- Density altitude
- A dramatic change of the wind direction
- Rotors over obstacles
- Engine losses power out of ground effect

Above can contribute to accidents but are given incorrectly for flying behind the curve.

So back to the question how do you avoid it in a Gyro??

[Learjet]

Discussion on this subject and a good video depicting a behind the power curve accident here: viewtopic.php?f=20&t=12178

As for avoiding it..I guess the cameraman's comments pretty much sums it up

[Gyronaut]

In my humble opinion t-bird, Airspeed Airspeed Airspeed! ... and adequate altitude to maintain airspeed to get yourself out of the tight spot you got yourself into in the first place.
I think my students hear it in their sleep.

[t-bird]

Agree on the airspeed.

But what if the variables change.You fly down to the coast , with the thicker air your prop is too course for the turbo to kick in. Your passenger looks a lot heavier than previous night when you met her after a few captains an coke.

You would not know that you would run out of runway and would be tempted to force the gyro into the air.

At wat stage of your take off do you abort?

[Gyronaut]

Very good point t-bird

The only thing that is certain, is that the variables WILL change. Constantly and sometimes instantly. For example, a magneto fails at full throttle and your engine is only running on half the plugs - your turbo doesn't kick in either! (I never knew that until it happened - the revs simply do not get high enough for the TCU to do its job).

Most certified aircraft have published take off minimums and their pilots calculate the weight and density altitude etc to determine the latest rotation point. They often use the distance between runway lights, then count them down - if they get there and they have not rotated or reached their published V speed, they abort. We have few of these tools at our disposal (runway lights? ). We mostly do it on gut feel which means we will get it wrong at some point. Not good. I am sure there are many different methods but my own one, for what its worth, is to mentally divide the available runway into 4 quarters in my mind. If I am not at V2min by half way, and not positively climbing by the end of the 3rd quarter I will abort, leaving me one quarter to cut the power and put it down. We do have the advantage of a HUGE disc shaped air brake to assist in stopping us very quickly when the stick is full back.

I doubt there is a standard published rule of thumb on this - the secret is to err on the safe side. If there is any doubt, there is no doubt. Don't. There is no shame in aborting the take-off and living to tell the tale. Similarly, I feel there is no shame in a go-round. I secretly admire pilots that go-around rather than those that force the landing after a bad approach - and yes, we all have them at one stage or another.

I am sure there are far more experienced pilots here that can add their input or chosen method and I agree, it would be nice if there was a simple way to decide in a gyro. Read up about Vef and Vfto speeds for conventional aircraft sometime. Its a whole subject on its own.

Oh and one more thing, beware of grass strips. I have often been surprised at how much longer and further it takes to get airborne off a soft grass strip! Be doubly afraid if the grass is wet!

Len

[MAGNIficent]

T-Bird

I also got the advice to use/test the TURBO often, even if you dont need it for take off. It happened that when in a emergency situation, you only find out it does not function properly.

[saraf]

I do not have allot of experience but , why do you want to put yourself in that position at all??

If you are not sure your gyro will be able to pick up the passenger , or that the density alt is to high, DO NOT FLY. It is easier to say no before the flight than to have to explain why you aborted the takeoff or crashed your gyro.

and again , if you get yourself behind the power curve , it is not the planes fault , nor density , nor your passenger, it is yours!!!!!!

Regards
JR

[t-bird]

Hi Eben

Agreed that you should not do it if you are uncertain.
We would not have any accidents if it was so simple.

In my example you are certain but don’t know that your turbo won’t kick in due to the thicker air at the coast.
You also trained at altitude and the drag of the rotor due to thicker air is a lot more than what you are used to.

Gyronaut I am also using the 4 quarters rule.

What speed do you use for V2min ?

Magnificent

The turbo on the 914 will not kick in at the coast if the prop was set correctly at altitude.
How do you test your turbo if you just landed at the coast when the sun was setting and the next flight is early morning ?

[MAGNIficent]

T-Bird give me a call and we can discuss the working of the TURBO at the Coast

zero 8 three 7 zero 1 00 seven eight

[saraf]

HI T-bird

If you are planning on flying to the coast make sure that your plane is then ready for the coast. Do not get there and then try and fix it or get it ready, This is just good planning. (yes I know it does not always work that way)

If you then get to the coast and you are uncertain , get somebody whom has flown at the coast to fly your plane and just feel it out, or go to Len or an instructor to show you the ropes if it is your fist time flying at the coast.

Again , good planning is essential. (ek weet ek klink soos n *&^%$ maar dit is mos maar die beste manier om n ongeluk ter vermy)

[THI]

T-Bird give me a call and we can discuss the working of the TURBO at the Coast

zero 8 three 7 zero 1 00 seven eight

No man! Share with us

[t-bird]

Hi Eben

The reality is that in South Africa you would take off at 5500 feet Grand Central and could end up at 50 feet Margate and the next day at 7000 feet over Lesotho.
How do you cater for this ?

Hi Magnificent

On a normal aspirated engine you will have more power at the coast – Agreed.

On a compensating turbo as the 914 you will get the same power on the coast than at altitude.

At altitude you set your prop by flying at 60 mph and getting 5800 rpm.

The turbo on the 914 only engage when RPM is I think above 5300 rpm. Don’t have my manuals handy.

It will also not engage if the air box temperature is above – a certain temperature – guys are usually caught out at Kariba in the summer

If you end up at the coast – the air is thicker

Thus more resistance on the prop

Your prop was adjusted at altitude for max power with less resistance.

You not getting additional power from the engine at the coast compared to altitude due to the turbo

The additional resistance at sea level will reduce the engine RPM

This means that you would not reach your 5300 rpm that the ECU demands before the turbo engage.

BOTTOM LINE NO TURBO

[Low Level]

MAGNIficent wrote:
T-Bird give me a call and we can discuss the working of the TURBO at the Coast

zero 8 three 7 zero 1 00 seven eight


No man! Share with us

Exactly my sentiments as well.

[saraf]

Ok T , ek verstaan daai een , enigeste opsie vir jou dan is

Koop n RAF , hy het nie daai probleem nie.

heheheh Groete
jr

[t-bird]

Eben ek wou al !