Postby alanmack » Fri Oct 27, 2006 1:28 am
Yes Bumble Bees can fly!
Helmet, headsets, winter flight suit, boots and a mug of coffee in hand saw me record 127kgs on a calibrated scale a couple of months ago.
Jenya Zozulya and I were asked the "can big guys fly a 503" question some time ago at Petit. Jenya must weight about 80kgs. His response was > We will show you and promptly took a rather concerned me to a 503 windlass with some 1500 hrs on the hobbs. With myself in command we took off at Petit and did a couple of circuits. The climb rate was adequate but not marvelous but I felt confident that we were not pushing outside acceptable limits. I did not try any steep turns etc and kept to my "own rules" see below.
My 100% standard 582 Raptor had an empty weight of 163kg per the plate on the engine frame with a 17sqm wing. With a standard Raptor wing I had no weight concerns in Johannesburg.
My climb rate at the coast has always been significantly better.
I have had 3 wings on my trike. The first with a standard 17sqm Raptor. The second was a sad example of what a Raptor wing can be. The second wing with a heavier trike but without a ballistic chute, two up, simply could not lift the front wheel off the runway. The third and current wing is an AEROSSA topless. This wing is wonderful! At the coast on a long flat beach I can (2 up) take my hands off the bar, increase power and roll without touching the bar, as I climb the bar moves forward automatically and the trike continues to climb until I come off the power when the bar comes back to a neutral position during which time I have not had a finger on the bar. This wing needs to be flown to be appreciated.
When I applied to do the proving flights on the topless wing (it was the first topless wing to be registered in SA) at CAA they insisted on a ballistic chute. Andy Kasperson at Petit did the technical inspections etc and the Raptor trike with the following mods: enlarged front forks, De Necker wooden prop, outsize "beach" tyres, leather seats & leather panniers, belly touring bag, high impact (solid) rear wheel axle struts, medical aid kit, tool kit, sea flare, radio, GPS, ballistic chute and the 85lt fuel tank weighed 238kgs without fuel. With a full tank it is just under 300kgs.
I trained on an Aquilla I at Ballito with Nigel Dorsett who must weigh about 100kgs.
I have done "Johannesburg" training with Mervyn Reynolds on his 582 Raptor with a 16sqm wing that also flies happily. Mervyn must weigh about 80kgs.
As far as the trike is concerned:
- I found that beefing up the strength of the rear axle struts and rear wheel axle stubs (more weight) was a good idea. If you land faster you will increase the chance of a "hard" landing. This will do two things. You will bend your root tube. If this happens replace it immediately. Secondly your rear wheels will flare out. You can bend them back but this weakens the wheel axle stubs.
- I have a flying buddy that is heavier than me and he had a second root tube fitted inside the standard root tube to strengthen his root tube which took care of this problem.
- You must hang your trike off the ground and have a new root tube drilled so that your front wheel hangs above the rear wheels. This means that a person of about 70/80kgs should not fly my trike as the front wheel will be way too high. Landing front wheel first is tricky and is not advised as you need to flare a lot more to keep the front wheel up.
As far as the pilot is concerned:
- Low and slow is out. You must keep your speed up.
- On takeoff you must execute a short field routine on even medium length runways.
- On take-off I keep my trike on the ground longer than most people and keep the bar in until I am 10mph above the stall speed. I then "bump it up" with a relatively sharp bar forward movement but only about 6in forward and then bring it back to keep the speed up well above the stall.
- Your risk of a stall is higher and you need to be aware of your air speed at all times especially when you do not have a headwind.
- Getting off the ground is unlikely to be a problem. The problem is to get through the "mid take-off" zone when you are off the ground but under 100ft AGL. As you go bar forward in the take-off you reduce airspeed. High climb rates on take-off look good but do not go there. If you do you will go into a stall and the trike will drop. In a cross wind you will slide to the ground. NEVER go bar out to climb and add throttle to recover under power when close to the ground. The chances are that you will continue to fall. If you go into a straight and level stall or a slide stall pull the bar in to increase your speed and then ease it to straight and level until your speed is up then climb out. Even if the coastal sugar cane or local mielies are up close and getting personal do not think that going bar out will give you the lift you seek. Bar in and speed will give you the recovery that you need.
- Practice low level flight and trike control just off the ground (3ft) so that you have experience in low level stall recovery.
- It's great to see trikes land on a ticky at or near stall speed. My experience is to keep your speed up. You need to practice near stall speed landings for emergencies but do this at the coast with a long soft beach in front of you where there is more bite in the air and near stall speed float is better. In altitude your near stall speed float can at times fall off alarmingly so keep your speed up.
- I was taught by two instructors two very different techniques. The first was to ensure adequate distance in the final approach. Slow the plane down with bar in neutral starting the final approach up to 500ft AGL then adjust throttle to aim your touchdown about 100m into the runway. 300ft is about the norm for fly-weights. At about 100ft max pull the bar in so that you aim to touch down about 30 ft into the runway. Your actual touchdown will be extended with your flare from about 20ft AGL. In the final "dive" ensure that your airspeed is at the very least 50mph (stall plus 10mph).
- The second technique is not much different in the explanation but very different in the "feel" of it. Essentially you keep more power to counteract a slight bar in postion to keep your rate of decent lower ie more power but bar in so that your airspeed is higher in the initial phase of the movement.
- I got so frustrated with my instructors when I was a student that I eventually sat them both down to sort it out. It was not long before I appreciated the two "approaches" and am thankful today. I use the first approach in calm winds and the second in high winds. In a high headwind you can easily find yourself in a stall, as you flare, if your airspeed is not sufficient. In high winds the "feel" is to fly the trike into the ground vs executing the normal approach.
- If you find yourself short of the runway GO AROUND do not try and extend your approach with a bar forward movement as you are likely to stall.
- With higher speed landings and bad brakes (even with new pads and after a service I have bad brakes) you need to brake to not overshoot short runways. To do this pull the bar in after touchdown as it will slow you down a lot. (One of these days I will treat myself to disc brakes).
- Finally never be complacent - that stall situation on landing and on takeoff happens very fast - always be ready for it and be prepared for the recovery routine. Always expect and be ready for a stall and you will ensure that it will not happen. I have had one brown trowser moment one up (cross wind slide) and another with Paul Lintott (about 80kgs) taking off at Emoyeni.
I believe that flying at MTOW or near the 450kg limit presents critical matters that require additional skills that must be taught to you.
Experienced pilots can adapt. When I flew with Demon in his GT450 I must admit that the instigator was Trixie Heron and I tried to explain that it would not be a good idea however the opportunity saw me having to tug at the seat belts to get in. We took off in about half my normal takeoff roll and climbed out at 600ft pm. It is an incredible piece of kit but without pilot capability the kit alone will not do it for you. I will go so far as to say that the pilot's ability and training has more to do with what you should be concerned about than what trike combination you should be looking at.
I have not had the following experience in an Aquilla and not with my Raptor with the topless wing. I have flown a trike that reacted very badly to MTOW. In this trike when I released the bar in a neutral position, at cruise speed, the bar immediately jerked forward and hit the profile tube as the trike went into a stall. I had to fly bar in with extra power and the trike had little float in the flare causing a hard landing. Beware of the fact that not all trikes rated at 450kg can, in fact, fly safely at MTOW. This experience I believe illustrates that the wing is critically important and you should not only focus on the engine selection. The GT 450 is I believe a 13sqm wing but the 912 provides the extra thrust. "Rockets have no wings but big engines!"
To summarise my advise to you is as follows:
- Do the weight watchers thing if you must but shedding 20kgs is not going to change your weight risk profile significantly > what is critical is that you must learn some basics - well.
- Find an instructor that has a lot of experience with flying at MTOW.
- Resist accepting your MPL until you have flown in all weather conditions and you have done a number of hours of circuits on "new to you" airfields.
- Have your "seat load" increased by getting your front wheel hang position lifted.
I hope this helps and would much appreciate advise from any quarter that is constructive and reduces the in flight risk to us Bumble Bees that simply must fly!
NEMO
I have now joined the ranks of wannabe pilots!
