Level flight before the initial climb

[Jean Claude]

I understand that the Magni M16 flight manual recommends to wait 60Kt leveling before climbing, when there is no obstacle.
However, CFIs recommend this too, even when the surroundings are crowded with trees.
I simulated the speed / height gain at take-off from a Magni M16 (115 HP) to 450 kg.
The calculation suggests a contrary result.
Comments? Thanks.

 

[twistair]

JC, gaining these 60 kts is needed mostly not for best rate of climb but for safety reason - to avoid entering "dead man curve". This is very important before you reach safe altitude. At 45 kts and, say, 15-20 meters of altitude pilot has no chance to land safely in case of engine-out. I use to demonstrate this to my students during their first flights - how fast things go bad in such situation. One such demonstration often saves hundreds of words =)

 

[Vance]

In The Predator (1,400 pounds maximum takeoff weight, 160 horsepower) if a client lets the nose get to high she can lift off early and I teach them to lower the nose to pick up airspeed before climbing out.

I recommend climbing out at 50kts indicated air speed and her best rate of climb speed is around 45kts.

I regularly practice engine out on takeoff from about 50 feet above the ground with no issues as long as I have at least 40kts of indicated air speed.

The lower the airspeed the more aggressive the round out and flare needs to be to have an elegant engine at idle landing.

The Magni M24 I recently flew seemed to want to stay on the ground till I urged her off. I only flew her for an hour in very windy conditions so I did not explore the speed range near the ground for simulated engine out on takeoff. Her best rate of climb speed was around 55kts.

In gusty conditions I like to get away from the ground at around 45kts in most of the gyroplanes I have flown.

Most of the training I do out of Santa Maria is at a density altitude of less than 1,000 feet mean sea level (MSL).

 

[Tyger]

It looks like your graph has it achieving 45kts in about 6 meters of roll, but then a further 130m to reach 60. That doesn't seem right to me.
I have only a 912, but mine definitely needs more than 6m to hit 45kts, but then I'm pretty sure I hit 60 well before 130m.

 

[Jean Claude]

This is not what this graph shows, Tyler.
The 0 of the graph is the position where 45 Kt is reached after the takeoff marked "T.O"
The rolling and the T.O preceding 0 is not quantified here

 

[loftus]

I agree with Tyger, from the graph it does appear that it takes an additional 130m to begin a climb if one waits till 60 kts is reached. I think both approaches 45kts or 60kts could be appropriate under different circumstances (and variations in between), given the pilot's experience. An approach that levels the nose and allows the speed to build after liftoff is clearly a safer approach to avoid getting behind the power curve particularly for an inexperieced pilot or in high density altitude or higher load conditions etc. On the other hand a climbout at 45 knots may be appropriate if necessary to clear obstacles etc, understanding that one has a much lower margin of safety as others have stated. Don't think there's a right and wrong here.

 

[Greg Vos]

I have done a 1000 + hours in Magni.... it's a very forgiving machine, on a short field take of 44 mph is more than safe, big thing is to calculate your distance to an obstacle (MAUW, DA, RW surface to mention a few)
In many real world situations one cannot always follow a book, once you master the craft one needs to fly it from the seat of your pants, and unfortunately this to comes with exp

If you don't have exp then fly it by the book but a more forgiving and easy to fly gyro.....has yet to be built!

 

[Tyger]

Thanks for clarifying, JC.
Actually for a "short-field" takeoff, the way I was taught was to briefly put the nose wheel back on the (hard-surface) runway at takeoff rpm (just as it starts to lift); by doing so, one gains airspeed VERY quickly. At about 65mph (57kts) mine then fairly zooms off – practically by itself. I'm pretty sure that going from 50 to 65 (mph) happens in less than 100 meters. This is all assuming no headwind, of course.
I'm usually flying off turf, however, in which case I do try to get off the grass quickly and fly in ground effect for a while before getting to that 65mph, which is more like what I think your graph represents. But as my instructor used to say, "soft field" and "short field" is usually a bad combo.

 

[C. Beaty]

A gyro always breaks ground before the rotor is fully up to normal flying rpm. That’s because normal flight rpm requires all the weight of the gyro be applied to the rotor. This requires a few seconds.

During the initial liftoff phase, it is better to keep the gyro in ground effect, allowing both rotor rpm and airspeed to build. If a climb is initiated during this phase, the increased load applied to the rotor may retard its rate of rpm increase and might even lead to catastrophic rotor flap.

This sequence of events is clear with analog rotor tachometers but is not so obvious with digital rotor tachometers and their blinking digits.

 

[Georgi]

Chuck , last sentence tickles me (as always). I see you standing on the podium of "whatever" University in front of thousands of graduates and tell them : down with "zeros" and "ones", boys and girls. There is a real world out there and you can feel it without microprocessors. Your twisted aluminum strip (aka. prop) for the airspeed indicator did not need any temp, density,altitude and ...microprocessor compensation.
Always Good Luck. Georgi.

 

[C. Beaty]

Georgi, I am not a digital circuit designer but I developed the first digital rotor tach for gyros in the 1970s. I can manage binary arithmetic and used a quartz clock crystal that runs at 32768 Hz, derived a 5/9 second count window using long chain digital dividers which is required for the 108 tooth prerotator ring gears in use at the time. Spinning at 1 rev/second, 5/9 of 108 = 60. 1 rev/sec = 60 rpm.

I made several of these things for friends using peg board and Ken Brock had my design put on a proper PC board and had then listed in his catalog. The Red Lion digital tach eventually came along and ended that foolishness.

But I personally didn’t use a digital tach except long enough to decide that I didn’t like digital rotor tachs and blinking digits. I’ve always used 0-50 mph motor scooter speedometers, with cable drives properly geared to run off the prerotator ring gear.

Unfortunately, propeller airspeed indicators indicate true airspeed and flying machines fly in accordance with density airspeed. Fortunately, aircraft ASIs are analog and indicate density airspeed; the downside being that when used with a vibrating Mac, most people ended up with a can of loose brass gears.

How have you been Georgi; still in good health? It’s been a long time since we last met.

 

[Jean Claude]

You're right, Chuck. : Takeoff is obtained before the steady rpm.
But starting my comparison from steady rpm, it seems to me that waiting 60 Kt instead of 45 is a bad choice to overcome the 50 feets hurdle.
Here, calculated for my tractor project:

Greg, and Tyler, thank for confirming that 45 kts is safe at AUW 1000 lbs.
Even without experience, the jump of an close obstacle at 60 Kt as drawn, seems to me less effective and much more risky than a calm climb to 45 kt .

 

[twistair]

I regularly practice engine out on takeoff from about 50 feet above the ground with no issues as long as I have at least 40kts of indicated air speed.

The lower the airspeed the more aggressive the round out and flare needs to be to have an elegant engine at idle landing.

I'd like to add two things which must be kept in mind:
1) decent speed for safe landing from low altitude widely depends on gyro model, take-off weight and density altitude. There is a huge difference between, say, MTOsport with one pilot and a Cavalon with 8.40 rotor and two heavy bodies in it.
2) it also depends on what is aircraft pitch angle when its engine quits. Most POHs which have dead man curve imply that pitch angle is zero, but when engine quits in initial climbs this pitch angle is always positive and this makes big difference since time and altitude will be additionally spent to lower nose. The more aggressive stick is pushed forward to lower nose - the more deep rotor unloading follows this movement, and the gyro sinks down more rapidly. This is what I meant speaking about keeping enough airspeed at initial climb. If aircraft pitch is level then it usually is possible to land it safely from any altitude even if its airspeed is a bit lower than best rate-of-climb airspeed. But once its pitch is positive then things go significantly worse. It also depends on how good is gyro's aerodynamics, in other words, how good is a gyro in gaining an airspeed in motor-off descend. I once tested an ugly and heavy gyro designed for AG-spraying - it didn't want to gain airspeed in engine-off descend at all - if only you literally push it nose down almost vertically. It is good that I first practiced this in that gyro since some flights later I had a real engine-out in it at about 60-70 meters altitude. A little more gentle (read: non-confident) stick forward kick would definitely ruined the day. Take care and fly safe

 

[C. Beaty]

If you’re trying to clear an obstacle, use the best rate of climb airspeed; ~45 kts. If you’re planing for an engine failure, more airspeed is the better.

 

[twistair]

I was taught that taking off towards an obstacle is a bad omen and may be performed in very rare cases only. This habit - not to lift-off towards an obstacle - saved my day on already several ocassions. Anyway in most cases when one has an obstacle on take-off direction there often is an option to make 180 deg. or 90 deg. turn right after lift-off and to climb without a concrete wall in the face.

 

[Tyger]

I would imagine that, if one IS taking off toward an obstacle, it's probably because the winds strongly favor that direction, which would certainly help matters.