Wednesday, 1 October 2008

The first 100 days. Part II

In Part I, I covered my reactions to flying the –4. Here I thought I would summarise my thoughts about the results of the decisions I made along the way, and the problems I ran into during the first 25 hours of flight test.

Many of the decisions related to weight. I have covered my thoughts and the result elsewhere in the blog, so I wont repeat that here. Needless to say, keep it light. Whatever it is, if you think long enough, you probably don’t really need it. Without it you will be lighter, have more money in your pocket and what you dont have can't go wrong.

The first issue I had was with the 4-pipe exhaust from Larry Vetterman. Pipe #1 just touched the sump. Larry first suggested I bend it, but as soon as that was not going well he said “…best I make you a new pipe.” It was here in the UK in no time. Great customer care! The 4-pipe is undoubtedly slightly noisier, but friends say not a problem. They also comment it has a very distinctive and pleasant tone.

Oil Pressure. I am delighted with my engine from Aerosport Power, and I cant imagine better service, but it did come with the oil pressure set too high. I had to reduce the pressure by about 10 psi, which was about 3 turns of the adjuster, to get it to stay inside the upper limit (90psi). The problem isn’t so much adjusting it though, as deciding if the problem is the pressure, or the gauge. In the end I managed to borrow a test gauge, plumbed it in, and it confirmed my ACS 3400 was right on the money. It was disconcerting on a new aeroplane though, until I got is sorted.

Oil temperature. The oil runs cool. I am not sure I have yet seen more than 179F. I have blocked off much of the entry to the 3” SCAT that takes air to the cooler. This appears to have improved things slightly but I need to do some more flying before I am sure.

I decided to take the exit air from the cooler into the cabin for cabin heat. This is working quite well, though its still only autumn in the UK.

With an electric heating pad in the seat, I think this will be quite adequate. It might yet cause me to put a variable restrictor on the air to the cooler.

Oil Leak. I had a significant leak on the cooler, for no other reason than I had failed to tighten the fitting adequately.. It did not show up after the first brief ground run, but it sure did after I landed from the very first flight. I probably only lost a quarter of a pint of oil if that, but a little goes a long way!

For the first flight I had a very heavy left wing, but a temporary trim tab on the rudder reduced this considerably. I was left with a slightly heavy left wing so I put a small coffee stirring stick on the underside of the right aileron.

This has balanced things up for now.

Sometime I will squeeze the RH aileron which will get rid of it due to the ‘Kutta Condition’. If you want to understand why that works there is an adequate explanation here.

VANS 'heavy wing' article which is worth reading if you have the problem is here.

Rubber Wing Root fairing. It was slightly disconcerting when these came loose in flight. A dab of RTV appears to now be holding them securely to the metal fairing.

I found the AoA in the AFS3400 hard to set. Just me I think, being ham fisted. In the end Rob Hickman gave me the file of settings for his –4, and that has worked well for me ever since.

A small leak in the static side of the ASI had a remarkably large impact on the indicated speed. It was quite frustrating to track down, but I got there in the end. Since the leak was to cabin pressure I was surprised by just how much this must differ from the ambient pressure. Even now, the system over reads slightly, but I put this down to the less than satisfactory rivet heads that VANS use.

The most frustrating thing of all was the intercom. Having indicated my interest in mono, with stereo would be “nice to have”, I got no suggestion from PS Engineering that I needed to allow for this in the wiring. I would strongly recommend people to go to Flightcom, since their documentation and understanding is far superior. They even supply the little switches and labels you need. The story is in fact much longer, uglier and expensive than that. Never an apology from PS for all the grief and expense they caused me, though I am pleased to see they have updated their FAQ to reflect the issue.

The Skytec LS starter bent its bracket after just a few hours of use. Aerosport Power had a new starter shipped to me in no time, and chose to replace the LS with the NL model at no extra cost. This is a much more serious looking piece of equipment. The LS normally has a problem when the engine kicks back, but since the P-mags retard when starting, Skytec guarantee the LS unit against this. My own view is the bracket is just too weak for a new engine with good compression, and a fully charged battery with a low resistance starter circuit. Who knows?

The dual P-mags have run faultlessly to date. I have little paper tell tales, that change colour if they overheat. Overheating has been a problem on some installations. They are still white. In the interest of simplicity I decided not to install a fuel primer, and rely on the carburettor pump to prime the engine. 3 strokes of the throttle, both P-mags on, and she starts really easily. Lets see what happens come the winter.

My oversize tyres work well. Near my hanger I have some gravel which I have to pull the aeroplane over. The –9a with the standard tyres I had, used to sink in and get stuck. With these, its not a problem. Despite their size they fit well inside the wheel pants, and to date they are not getting clogged with either the output from these sheep, who mow the runway, or mud.

The 2-blade MT prop is a delight. Really smooth in operation. The governor had to be very slightly adjusted slightly initially to stop it over speeding. Now it maxis out just below 2690. My only reservation is that it would be easy to scratch target="_blank"in the hangar. I am quite clear a 3-blade would have been a big mistake for the reasons I gave before.

The current outstanding issues are:

  1. I would like to get a little more cooling on #3 and a little less on # target="_blank", so I am playing with a baffle to push more air over the top of #1.
  2. #2 CHT can run a little hot, and the EGT cooler than the others, so I am wondering if I have a tiny induction leak, or if this is the variability of a carburetted system. Next time the lower cowl is off I will have a good look around at #2 induction.
  3. Taxiing I have a very slight rattle in the gear. My thought was that it must be the gear leg fairing moving wrt the wheel pant, but a friend has suggested possibly the brake callipers can rattle. I will try taxiing with the brakes gently on.

Finally, I would just like to say what excellent and warm service I have had from Aerosport Power, E-mag, Robbins Wings, Larry Vetterman, AFS, Becki Orndorf who made the seats, and John Stahr, who painted it.


  1. Congratulations with a nice flying and nice looking airplane.

  2. Very nice write up.......keep up the great work..!!It helps us all...

    Paul Gagnon

  3. Thanks Stephen. Great blog! As in everything aviation, testing components and systems ultimately makes aviating safer, especially for the experimental category.