High winds/no prerotator

Resasi

Gold Supporter
Joined
Jul 2, 2007
Messages
9,088
Location
London/ Kilifi Kenya
Aircraft
Gyrs, RAF 2000/Mgni/Bnsn/Hrnet/Mrlin/Crckt/MT-03/Lyzlle AV18-A/Prdtor. GT-VX1&2, Pax ArrowCopter
Total Flight Time
100+ gyro, 16,000+ other
I know that some of us fly without prerotators and am interested in any other observations from those who do. Here are what I have found recently as the last few weeks have tended to be very windy.

Early on I had experienced problems in no-wind conditions when trying to pat up the blades on my own, discovering that having patted up as fast as I could go I could not spend any time fastening in but had to move off immediately in order to get some airflow to build up RRPM sufficient that would allow me to stop and do up the seatbelt, a slightly fiddly 4 point harness, before proceeding to get them up ready for a take off. When beginning to get to full back stick increasing power in this low wind situation also helped to feed air into the tip section of the rotor as it starts entering the prop slipstream.

Gaining experience in higher and higher winds I have now found that point can be reached where even when strapped in and having someone else patting them up to as high an RPM as they can, when you back stick to let them exit from the front, the wind can be strong enough to crowd your blades and begin blade sail/flap almost immediately because it exceeds the ammount of air for that RRPM.

In the case of patting them up on one's own over a certain wind speed, and it will vary with your particular blades, and definitely not DW's, it does get tricky feeding the wind into the rotor by slowly coming back on the stick, particularly if the wind is gusting. Here since you do not have to full back stick to let someone out, you can take your time over this.

With winds of 8-13Kt approx it has not been a problem, but as it begins to approach 20 Kts the feeding in of the wind does start to get a lot more delicate an operation if not almost impossible.

Over 20 Kts I found that after a lot of trying I had to go back and move into the lee of the hanger to reduce the headwind before I could then manage to get the blades spinning fast enough to then move back into the full wind.

Not having a RRPM indicator does make this a bit more tricky but when flying the simpler gyros a lot of this is done on feel anyway.

Flying in strong winds is great fun and building up the experience has taken time. Obviously it is more critical and I am very conscious that one is continually learning, hence the interest in hearing other peoples experiences on what to watch out for, pointers and tips.
 
I had to develop a one-legged stance on the seat of GyRonimo in high winds. I used the other leg to push the cyclic forward. Now that is an acrobatic maneuver! Once I had the best spin I could muster, I let the cyclic move back (due to the trim spring) slowly and dropped down into the seat immediately. The next issue to be aware of before engine start was that the rising rotor speed and lift would defeat the brake and drag the machine backward. This could be avoided by pushing the cyclic forward. Engine start was the next imperative. Then connecting the belt and radio and other fiddly bits.

I don't believe in spinning the rotors up with the engine running. It does make the startup in wind fairly complicated. I did a lot of practice to develop a routine that worked for me.

There is an example of this one-legged startup from Bensen Days 2008 in this video at about 2:10:

YouTube - Bensen Days 2009 Various Gyros
 
In high wind conditions, turn the machine tail first into the wind and let the wind blow through the top of the rotor.

It might now work on highly cambered blades (flat bottomed) but works very well on symmetrical and mildly cambered blades.
 
Yes Jon I watched you starting a couple of times and admired your agility, I am beginning to freeze up a bit on the joints and not so nimble. Good point on the brakes and rolling back, the Bensen brakes are not that hot and I sometimes have to juggle stick and throttle sometimes to hold her in position

I guess that overhead start of yours works pretty well, fires up right quick. The 532 over here is very good at starting, the 503 in Zephyrhills a little less obliging, perhaps I haven't got it set up quite right. They both pull from the side.

Thank you Chuck for pointing that out, I must confess I did not think of trying that, although at time when taxiing with the wind behind me I did not notice it speeding up the blades appreciably. The Rotor hawks are flat bottom blades and so it may just be that.

I have to say I would be a lot more cautious in strong winds with the DW's with or without a prerotator until I have a lot more experience with them.
 
Resasi said:
Yes Jon I watched you starting a couple of times and admired your agility, I am beginning to freeze up a bit on the joints and not so nimble.

That's not agility. It is merely the result of practice, coupled with an extreme desire not to end up upside-down on the pavement like a turtle and making a fool of myself. Or at least providing absolute proof that I am a fool for those who already suspect.

Besides, you were probably too far away to hear all the joints popping and creaking. Most people just mistake that for noise coming from the gyro. It is actually pretty quiet until the engine is started.
 
Especially on windy days it is a good idea to bring along a bungee to secure the stick when needed (kept in its own zippered pocket of the flightsuit)
 
I like that thought George. I always carry the rotor tiedown with me but a stick bungee would be a useful thing to have under these conditions.

I seem to remember that Birdy has a built in stick lock on the Ferel.
 
I seem to remember that Birdy has a built in stick lock on the Ferel. Never fly without one Leigh.
Wether iv got a prespinner, rotor break or both or nun.
 
What blades are you using Leigh?

Aussie Paul. :)
 
Paul, on the Bensen 23' Rotorhawks, and on the Hornet 23'Dragon Wings.

The Rotorhawks I felt were an ideal training blade, especially for learning patting up. They either flap or they fly. The DW's definitely have a better performance. Students here have been fine with Dragon Wings with prerotators, but we have had a couple of instances (funnies) with at least three people I know with DW's in flight.

One got airborne with flap...for a little bit, Tony, and he admits that was his fault plain and simple. Another who I and others were watching got airborne then found it simply would not climb, flew the length of the runway, I thought he was just gaining speed for a nice impressive climb away but just hopped over the hedge at the end of the runway and then eventually climbed away quite sedately having scared the .... out of both us when he dissapeared, and himself. He on his return suspected he had been in a semi flap for a bit.

And one student who was doing long hops and was being watched by some experienced guys, Tony was one, and they said they were sure that the blades had been in a semi flap for his last hop. When he came back he said it had 'felt funny'. I have never experienced anything like this but have a lot less time with the DW's.

I have briefly tried the McCutcheons on the Bensen, they felt very nice.
 
Very interesting, I'm learning from this.

Thank you buddy for posting it!
 
whats your disk loading with the rotor hawks leigh? 20kts of wind unless laminar flow in a gyrobee would be approaching a rough ride. terrain around here varies from flat cotton fields to very wooded with very tall trees depending on where you go.
 
Jeff with me and 5galls at a 1000' the disc loading is around 1.35.

We have fairly undulating countryside with hilltops at around 700' -800'. Fields with wheat, rape, horse and sheep paddocks. Scattered woods. Pretty mixed. There is some rolling turbulence from the hills and it can get bumpy at times.
 
rotor foreplay;

rotor foreplay;

Leigh, I'm surprised you dont have a digital rotor tach fitted.
Cost is buttons. Weight is feathers. If Tony prefers students to not use it so students develop a better 'feel' for the rotors, it can be unclipped.

At the low end, in dodgy conditions, (flat calm, or light wind with gusts), it can be very helpful in establishing whether you are gaining or losing RRPM.
I'm talking about the difference between, say 45 and 47 rpm, and the trend.

At the high end, you should know your cruising RRPM fairly precisely, so you can pitch your rotors for optimum cruise or optimum ease of prerotation, or
the best compromise.

Examples, as relate to my machine;

Cruise RRPM 360. Prerotation reasonable from 40.
Cruise rrpm 380. prerot possible from 30. Poorer rate of climb due to energy being consumed to spin rotors faster.
Cruise rrpm 320. Prerot harder, from 45. Improved climb rate. Probably safer in the event of a rollover.

If you have plenty of spare power, lower the pitch on your blades and make
life easy on the arms.

Without a digital tach, you are unlikely to know where you are on the scale
of possibilities.

I dont yet fly in 20kt winds, but in gusty light winds I do.

You probably know all this already, but you asked, so there you go.

Had a bit of fun the other day, bringing up the blades from 90 or so, without
using the prerotator, in Helipaddy's ELA.

P.S. My blades are 23' extruded RotorHawks. AUW about 560lbs.

Cheers.
 
P.P.S. In calm, or very light breeze, I also spin up to about 75, then belt in.
Just so long as you remember to, I guess it's safe enough.
 
Fergus, the lack of rotor tach is sheer idleness, have been intending to put one on for a while. You are quite right there has been no reason not to put one one and I would agree with you wholeheartedly in gaining an very useful instrument.

As you say the pitch of the rotor is a compromise between patting up and cruise performance with us here as we have scads of take of room so it is not take off distance. I am never in a hurry to go anywhere fast, very happy pottering around at around 45Kts most of the time although it will cruise at 55-60 at full throttle. So it has principally been ease of patting up that has taken priority. I suppose in the beginning having got used to doing without a rotor tach have never really missed it but it will be going on shortly. I was looking at one the last time I was down at the hanger.

Thank you for your figures, looks like we are about the same so they will be quite handy when I start working with them and experimenting with a rotor tach. Up till now I have always rather been flying than fiddling around with rotors and the rest. I am not a keen builder or tinkerer, whatever gets me in the air I will then work with. Upgrading to the 532 and four blade Arplast certainly did wonders for the performance, but certainly not a surplus of power.

The higher winds really do bring out the potential of the gyro to perform more like a helicopter, and, I find, most interesting to work with. And right now with the low temperatures performance is good.

Yes early on Tony once set me an exercise in the RAF down in Henstridge while we were sitting waiting for traffic, and I managed to bring the blades up from quite low to around 90 just by feeding in the wind. Another early student exercise was just sitting in the single seat gyro bringing the rotor up to as fast as it would spin with the wind only.

Hope you had fun with Paddy, hope the school is doing well. the ELA looks as though it would be a fun machine. I have been lucky enough to try the MT sport and Magni 16, so an ELA at some stage would be interesting.

As for belting in, having automatically done it for so many years, I feel naked without them.
 
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