Monday, 22 September 2008

The first 100 days! - Part I

The first 100 days with an RV4! What a blast its been. This is the second VANS aircraft I have built. Last time I was disappointed, I built one of the designs for geriatrics, this time I am ecstatic. I thought it might be useful to other -4 builders, to gather my impressions and experiences while its still all new and fresh in my mind.

As I was building, I had to make many decisions that would have a bearing on its future utility, and as I moved towards the first flight I had many queries as to how she would handle.

Details of my -4 are covered in much more detail elsewhere on my blog, but G-IKON is powered by an Aerosport Power O-320 160 hp engine, driving a two blade MT c/s prop. She is the first aircraft in the UK approved to run on twin P-mags.

I’ll start with the flying, because that is what this is really all about, but then cover my experiences with some other items in Part II. Before I start I should say I have over 400 hours on Supercubs, and more on other taildraggers, so tail draggers are not strange to me.

To date I have about 29 hrs on G-IKON so am far from experienced. I have just finished a much longer than normal flight test because of the P-mags. Because of the flight test I have only once flown 2 up. I have only flown on/off grass so far, so all-in-all, plenty yet to learn.

Takeoff. I have a flap position indicator on the wing. Early takeoffs I set this to around 10 degrees, though I now set around 15, and find this may be marginally better. This gets me off the ground in about 300’ which is VANS number. I had seen tail dragger RV pilots have quite a bit of a problem with torque steer as they initially put the power in, but I have not experienced this at all. I do find a distant tree or cloud to focus on, so perhaps this is the reason. I am not aware of putting any rudder in, but some say I must.

By the time I am off the ground I start putting the flaps away, and start the transition into the climb as soon as I see 100 mph. Below 100 she is very draggy. This speed comes up about 1000’ after the start of the takeoff roll. My immediate reaction on the first flight was one of a solid predictable and responsive aircraft.

I feel I still do not make quite the clean transition from rolling to flying that I would like. There always appears to be an instant when we don’t quite know which we are trying to do. Perhaps I think I get a message saying its time for flight half a second early. What I have found is that its best to get the tail wheel off the ground ASAP, but then leave the tail low, so once we are flying, during the acceleration I am actually pushing ever so slightly forward as the speed builds, until its time to climb.

Landing. My home runway is short. Fence to fence is 1020’ and it has many other complications. Confidence to return to it, came after 27 landings at a local grass airfield where we got to know each other, after the initial take off from my home strip. I still don’t quite believe it, but a –4 is a remarkably easy plane to land compared with a Supercub, and needs about the same landing distance. I typically use 600 to 700’. At first I struggled a little doing 3 point landings, which didn’t always work so well. The problem was the tail wheel would hit a small bump which would throw it back in the air, sometimes worryingly high. Now I flare until the tail wheel is, at a guess, just 3” off the ground. That so far has produced a winner every time. Not to do quite fully held off landings has been quite hard to learn, but she still lands nice and slow. (I should qualify this. Landing two up is completely different, though I have only done 3; very ragged. I havn't cracked that yet. Its a completely different aeroplane! As the speed bleeds away in the final second, possibly it needs a push on the stick to hold the attitude. Perhaps its just very light. It has caught me out each time somehow.)

I said easier to land than a Supercub. This is true, but I suspect much less forgiving. Partly for that reason I have an AFS AoA installed, and I expect 'Jennifer' to give me a good talking to, if I fly abusively slow. So far she has only done it as the wheels touch. "Angle, angle, push!"

Somewhere in the circuit, with full flap, I trim for, and settle at 60 mph, solo, and let that start to bleed away just before the fence. She is still very ‘solid’ at that speed. I approach on the flat side which requires quite a bit of power, but I find that helpful, since as you start feeling for the ground, as soon as you are confident there are only inches between the wheels and the grass you can shut the throttle and she gently settles with no intention to bounce. I usually lift the tail once the mains are on. I can see better, my strip is narrow, and the rudder is more effective, though I still find myself using differential braking.

I have little cross wind landing experience with G-IKON so far, but the one I had to do went well. I crabbed the approach and converted to wing low quite late. This worked. Once on the ground, rudder, with the tail high, plus differential braking, enabled me to track as I wanted. As the autumn winds set in across my strip I will soon have much more experience. The equinox was 2 hours ago.

Cruise. Not a lot to say here. She is extremely exact to fly which is very pleasing. VANS say I should see 207 mph with 160 hp, and that, if you wait long enough, is exactly what she does. I have been breaking in the engine, so have far too much experience at high power in the local area. (I am limited during flight test to 35Nm from base.) In the last few days I have been hunting for a normal operating regime. Its beginning to look like perhaps 2300rpm and 23.5” which gives me a 180 mph cruise. 2200 rpm at 22.7” which leans out to about 24lph - about 6 little US galls. – and results in 165mph is also a regime I return to. I will be more exact about these numbers once I have been on some trips and have an established regime.

Handling in general. Fantastic, harmonised, delightful. I don’t know what else to say. If you are still banging rivets to build a –4, keep at it. If you are disappointed, there is something wrong with you. If you cant get in a -4, stop going to McDonalds. Do build it light though. (See 9/5/06 and 6/10/08)

I will come back with some more observations in Part II about the technical problems I had to fix, and how some of the systems have worked out, but that’s it for now.

1 comment:

  1. Congratulations on completing your aircraft! I am planning on starting an RV-10 in the very near future. I love to hear stories of completed RV's.