Gyro's vs Helicopters

[whirly]

Whirly, gyro manufacturers don't seem to have a redline or maximum rotor RPM. In a gyro, if you enter a steep turn, and load the rotor, the rotor RPM will increase, but before it reaches any serious RPM, if the steep turn is steep enough, the indicated airspeed will eventually bleed off - a total non-event.

In a glide in a gyro, flying too slow is absolutely fine, depending upon your height agl. I routinely approach over the threshold at 1500ft, slow the gyro down to zero airspeed, and allow the gyro to enter a vertical descent. At about 300feet agl, I then lower the nose to allow the airspeed to increase from zero to around 60mph so that the gyro has enough energy to flare and land. It confuses the fixed wing pilots big time when they see a gyro approaching from directly overhead the airfield!

FO Gyro,

"0" airspeed or "0" groundspeed?? My question is when you are doing a full autorotation (in case of a complete engine failure) in a gyro. Then obviously airspeed would be important? Would too low an airspeed not cause your rpm to bleed off in that case or can gyros do a completely vertical descend?

Gyros then obviously also can't get into vortex ring state like helicopters can, a very dangerous situation.

I am learning!!!

Whirly.

[FO Gyro]

t-Bird, when I did my initial gyro licence with Eric Torr, a good 10 yrs ago, Eric showed me some advanced manoeuvres. He showed me a spiral dive where you allow the airspeed to increase to 90-100mph, and then enter a steep turn simultaneously. You are quite correct, the rotor RPM will increase from 360-400RPM to about 550RPM!

I don't really know if this could overstress the blades too much. Maybe it could. I don't try this because it is a grey area for me. I prefer the other side of the aispeed indicator, ie. playing around at low speed (with sufficient height to spare of course). There is wealth of info on rotaryforum.com Maybe one should ask the forum members there to see what the concensus is.

[Trikenut]

On the subject of Gyro's vs Choppers:
For me.... It would be both!!!
No seriously, I believe they both have their merits, but a gyro is a lot safer and would probably be my choice! I am also very conscious about global warming and to fly around 1 up in a chopper burning all that fuel, would make me very guilty!
On the other hand, I am not so bad with the airliners as at least you are transporting +/- 300 people in the process!!
I am a Trikenut (Nutty about trikes) and I always thought, gyro's.... big woop dee doo. But after flying in them... let's just say: Maybe I should change my name to Gyro and Trike Nut!!

Ross (Trikenut)

[FO Gyro]

Whirly, gyro's can fly absolutely normally at 0 airspeed (not groundspeed). The only snag is they can't then maintain their height, and descend rather quickly when flying at such a speed.

Rotor RPM does drop slightly compared to that in the cruise, but then it stays at the slightly reduced RPM. A vertical descent is a completely safe exercise in a gyro! Airspeed is not important at all, whilst you have altitude in hand. As you get closer to the ground, as per the height/velocity graph, you need to allow the airspeed to increase to have enough energy to land. I have descended often from as high as 10 000ft all the way down to 1000ft, at 0 airspeed. It is the quickest way to descend as the rate of descent is very high (around 1800 ft/min with the engine delivering a trickle or power to keep some rudder authority).

[Low Level]

Too slow during a "glide" in a gyro should also be more dangerous than too fast?

I routinely approach over the threshold at 1500ft, slow the gyro down to zero airspeed, and allow the gyro to enter a vertical descent. At about 300 feet agl, I then lower the nose to allow the airspeed to increase from zero to around 60mph so that the gyro has enough energy to flare and land.

I've seen FO Gyro do this and must I add, very impressive - so much so that I have started practising it, and boy what fun.

Too slow during a "glide" in a gyro should also be more dangerous than too fast?

The only reason why you want to maintain 65 mph, is that is the speed for optimum glide ratio. If landing options are numerous, you worry about nothing, everything takes care for itself. Airspeed can be zero or 90 mph going down. Rotorspeed will vary within 20 or 30 rpm of normal. The only prerequisite is to get your airspeed to 60/65 mph for the final flare, and that can be done within the last 300 ft of descend.

[FO Gyro]

It's great fun to "hover". Quite a few gyro pilots fly their gyro's like fixed wings, and don't do the vertical descent thing that much, not sure why. Maybe the instructors don't teach it.

The only thing to watch out for is to make sure one can recover by lowering the nose only, and not using the engine. If the engine fails as this critical time, and one has left it too late, when could have a little oopsie.

I've had to limit my vertical descents at Stellenbosch airfield, as the "know it all" fixed wing instructors somehow get confused and don't appreciate my gyro's capabilities!

[FO Gyro]

Whirly, in the 1st photo, I'm doing 90 mph in my MT-03, rotor RPM is 370RPM, straight and level, VSI is zero.

In the 2nd photo, I am in an established vertical descent. I have reduced power, the airspeed has been allowed to reduce to 0 mph by back pressure on the stick, rotor RPM is now a constant 325RPM, and the VSI is about 1500RPM. At long as I have height to lose, the rotor RPM will remain at 325 RPM. The gyro is also perfectly controllable, and one can even yaw around the vertical axis! Because the gyro doesn't have a collective, there is no flare capability at all in this scenario. The only way to recover is to gently lower the nose, and to apply power again. As I mentioned, one mustn't leave recovery too late, normally 300ft at the latest is fine.

[Low Level]

The only thing to watch out for is to make sure one can recover by lowering the nose only, and not using the engine.

Good one to remember. Using the engine, the acceleration is quite violently, so I don't like it, and don't use it, BUT I must remember not to rely on it.

I've had to limit my vertical descents at Stellenbosch airfield, as the "know it all" fixed wing instructors somehow get confused and don't appreciate my gyro's capabilities!

Convince them to get in the gyro for one of those. They will then offer their humble apologies for taking that previlage away from you.

P.S. Nice comparison pics. - still at the good old Kitty - 120.65

[whirly]

Thanks guys!!!

More questions...............................if you don't mind!!??

How long does it take to reach 60mph once you lower the nose at 300' ? Is it difficult to lower the nose if the engine should cut? I see your rotor rpm arc is from less than 200 to nearly 400! That's a very wide range, choppers don't have that luxury.

I am pretty sure the rate of descend is much lower in a gyro than a chopper during a proper auto and that combined with the landing attitude is why you get away with not having a collective!!

Is there anybody on here that flies both??

Whirly.

[FO Gyro]

Whirly,

The gyro accelerates very quickly to 60 mph. What is quite alarming for a passenger not used to it is the sudden extra high rate of descent when one lowers the nose (one is already doing 1800 ft/min before sticking the nose down). Sounds worse than it really is. It's good fun.

Whether there is power on or off, there isn't really a noticeable difference in the ability to stick the nose down. Although the green arc is 200-400, I would think if you had a rotor RPM (not that one can control it) of below 300RPM you might be in serious trouble (just a gut feeling), so the normal range is more like 300-500+RPM (for those high speed spiral dives). The only way the rotor RPM would decay is if you had to violently unload the rotor by inducing negative "g". This is stricly forbidden. Even 0 "g" is limited to maximum 1 second. Unloading a gyro's rotors is a big no-no (similar to a lot of teetering rotor heads in helicopters).

[Low Level]

Is there anybody on here that flies both??

Jetranger has vast experience in both. Funny, with the crappy weather in Cape Town, one would think that he would spend more time on the forum.

[mikemat]

FO Gyro touched on it, but in my view the only really significant difference between a landing under power and a 'dead stick' landing (apart from the steeper approach angle always required to maintain speed in the absence of power) is the lack of rudder authority and consequently slow and sluggish rudder response which results. For the rest you have the same ground effect to cushion your landing as you would if you had power.

What I would like to know is what drills are required to put a heli into autorotation in the event of an engine out (eg - disengaging the rotor from the power plant, adjusting the collective (?) etc..), and what the difference is in the margins of height required to perform a safe autorotation in, say, a R22 as opposed to a typical 2-seater gyro. I would imagine that a much greater margin would be required for the R22 because of the loss of height sustained whilst executing the autorotation drills, and its greater weight. Comments? Len?

[mikemat]

FO Gyro touched on it, but in my view the only really significant difference between a landing under power and a 'dead stick' landing (apart from the steeper approach angle always required to maintain speed in the absence of power) is the lack of rudder authority and consequently slow and sluggish rudder response which results. For the rest you have the same ground effect to cushion your landing as you would if you had power.

What I would like to know is what drills are required to put a heli into autorotation in the event of an engine out (eg - disengaging the rotor from the power plant, adjusting the collective (?) etc..), and what the difference is in the margins of height required to perform a safe autorotation in, say, a R22 as opposed to a typical 2-seater gyro. I would imagine that a much greater margin would be required for the R22 because of the loss of height sustained whilst executing the autorotation drills, and its greater weight. Comments? Len?

[mikemat]

Sorry about the echo. Parkinsons?

[Learjet]

the only really significant difference between a landing under power and a 'dead stick' landing (apart from the steeper approach angle always required to maintain speed in the absence of power) is the lack of rudder authority and consequently slow and sluggish rudder response which results. For the rest you have the same ground effect to cushion your landing as you would if you had power.

Mike, whilst ground effect does play some role in 'cushioning the landing', the primary "cushioning effect" is created by the transference of rotor's kinetic energy into lift when one flares for landing. (Newton's 3rd Law / Coanda effect etc)
When landing in still conditions (i.e absence of headwind) you may find that a dead-stick landing will allow you to execute a substantially shorter or zero-roll landing compared to that of a power-on landing. The reason for this is that the steeper / faster nose-down dead-stick approach, (apart from maintaining airflow / rudder authority) will bring about increased rotor RPM which is thus converted to create more effective lift for the landing flare. To illustrate this point a 'close to the power-curve" approach - although having a much slower apparent groundspeed, will actually necessitate an increased rotor AoA in the approach and thus less rotor kinetic energy is available to convert to lift in the final flare. This results in a diminished reduction in groundspeed and thus a longer / faster ground-roll when landing.
The difference can be quite subtle or not even noticeable when landing into a nice headwind as the windspeed will obviously load the rotors when flaring (helping to create that extra bit of lift) and the increased drag will slow the ground-roll quickly. But in windless conditions the difference is certainly very noticeable.
Whilst power-on landings help maintain rudder-authority and the shallower glide-slope makes judging the flare easier, I always prefer to execute dead-stick landings for the reasons already mentioned - but also because this is what will be required in the event of an emergency landing - and the less ground-roll the better should you have to put it down in unfriendly terrain.