By Vic Syracuse, EAA Lifetime 180848
When I wrote last month’s column regarding the first flights of my new Hummingbird helicopter, I was just completing the 11th hour. As I write this one, I have just crossed over 30 hours. In most of the other aircraft I have built, the test program has been completed within a month, with the only delaying factor being the weather. I’m learning a whole new game with the helicopter.
I keep remembering something that Alex Anduze mentioned when we were flying together: I was more of a risk than the helicopter. That turned out to be true. It did take me time to get to know and be comfortable with the helicopter. It’s a new machine — and much bigger and heavier than any other helicopter I’ve flown. The controls are heavier, but I learned to aggressively use the trim. It’s now enjoyable in all phases of flight.
Meanwhile, except for a failed rotor tach generator, the aircraft has been reliable.
I have approached the flight test program cautiously and slowly, as we haven’t really developed an amateur-helicopter flight testing handbook yet.
A good part of what is currently in the EAA Flight Test Manual is not applicable to helicopters, such as stalls, accelerated stalls, best glide speeds, determining VX/VY, use of flaps, etc. Some things are applicable, such as taxiing (the Hummingbird has wheels), takeoff performance, and weight/CG testing.
Some things have been tested by the factory, such as autorotation speeds, and I am not nearly experienced enough to start testing to see if mine is any different.
My operating limitations didn’t give me the option to complete a task-based program, so even if I had one, it wouldn’t make any difference in the hour requirement. Truth be told, I’m quite glad for the 40 hours. Besides the flight testing, there’s a lot of tweaking that requires many short flights, such as adjusting the blade tracking. Plus, there are more frequent lubrication intervals, such as greasing the main rotor head and tail rotor every 30 hours.
So, here’s the approach I’ve taken. As I mentioned in the first part last month, I did quite a bit of hovering and runway flights prior to flying any traffic pattern. Then, as has been my practice on all test flights of new aircraft, I did not leave the pattern until I had completed five hours. I made the best of that time, performing fast stops, normal approaches to landing, including approach to hovers, and even full setdowns.
I also made steep approaches to landings. I did lots of hovering, in both calm winds and some strong winds up to about 20 knots. I was tickled that there is more than enough tail rotor authority to handle the crosswinds in those conditions, performing 360s both left and right.
I have also tested left and right sideways hovers, along with backward hovers. One of the things I noticed during extended ground maneuvers is that the carbon monoxide detector kept alerting me on the electronic flight instrument system display. I installed the detector underneath the seats in the lower cabin, and now I’m thinking that the source of carbon monoxide might be through the bottom of the aircraft openings for the cables and controls. I made a couple of flights with a Sentry detector installed on the windshield close to my head. It did not alert me, so now I am working on sealing up the openings.
I also need to continue some flight testing with the doors off. I had initially flown it with the doors off, but the weather got cold again so the doors went back on. With the doors back on and the cabin heat working, I also wondered if the heat was a source of carbon monoxide. So far it doesn’t seem to make a difference whether the heat is on or off, so that’s a good thing. I have not received any carbon monoxide alerts during cruise flight.
During my initial flights down the runway, I would accelerate to about 50 knots and then perform some fast stops. The best rate of climb was also between 45 and 50 knots, so that’s what I accelerated to for my initial climb-outs from the runway.
Looking back on what I’m going to share with you now seems funny, but it took me a while to figure it out. With more than 6,000 hours in Van’s RVs, I can always tell the proper climb-out speed by looking out the window at the pitch angle. Sometimes I’ve performed first flights during which the airspeed indication quit for one reason or another right after takeoff. It was really no big deal. With helicopters, the climb-out deck angle doesn’t really change that much. It’s kind of flat after the initial acceleration through effective translational lift.
The airspeed was locked on at 50 knots during the initial climbs, and I was proud of myself. However, I thought the climb rate was rather lethargic, and on downwind it didn’t accelerate much past 50. At that time, I was just happy it was flying and still making noise, so I didn’t focus on the speed. I was focused on staying close to the runway environment. I used the recommended 45 knots for approach, and all worked out well. However, from ground cues, things seemed to be happening a little fast. No mind about that now, as I was just focused on not screwing up.
There was also another piece of information floating around in my head. Another builder who had just completed his Hummingbird was complaining that his seemed really slow, which he wasn’t happy about. So now I had this nagging feeling that this helicopter was slower than advertised, which wouldn’t be the first time that has ever happened. However, I had just flown the factory aircraft and took pictures of the power settings and speeds, and had reviewed them quite extensively prior to the first flights.
After a couple of these circuits, I decided I had a few extra brain cycles freed up, and I compared the airspeed to the groundspeed. Wow, they sure were different. Since the helicopter had been running okay, I decided to do a quick 180 and check it in both directions. Guess what? The airspeed indicator was low by about 20 knots. I used groundspeed for the next approach, the visual cues looked more normal, and the transition to a hover was much more smoothly accomplished.
I checked the pitot-static system prior to the airworthiness inspection, and I now checked it again. The airspeed indicator and static system were dead on. Neither had any leaks. It didn’t make any sense to me until I noticed that I had checked the system by hooking in at the back of the Raven pitot tube, which had both pitot and static outlets. Sure enough, when I checked the pitot tube by itself, it leaked on both the pitot and static sides.
I spent hours trying to fix the leaks and finally managed to stop them. I was so convinced the airspeed would work properly on the next flight that I was shocked when it again stagnated around 50 knots. Now I was perplexed. I took a chance and disconnected the static connection to the pitot tube, and it then worked properly in flight.
I’ve flown next to two other aircraft and verified indicated airspeed within 2 knots and altitude within 20 feet. I’ve flown a GPS triangle and verified the airspeed indication as well. I replaced the pitot tube to no avail.
I’m thinking there is some airflow around the nose of the helicopter that is interfering with the static system. I’ve yet to figure it out. This is the first static system problem in my life that has gotten the best of me.
I’ll continue next month with the progress of the flight testing, which I will hopefully have completed by then. We are aiming to fly it to EAA AirVenture Oshkosh, so we hope to see some of you there.
Meanwhile, I assure you the fun factor is alive with the Hummingbird. It’s the most complex aircraft I’ve built — and there are days I am amazed that it is flying!
Vic Syracuse, EAA Lifetime 180848, is a commercial pilot, A&P/IA mechanic, designated airworthiness representative, and EAA flight advisor and technical counselor. He has built 11 aircraft and has logged more than 10,000 hours in 74 different types. Vic founded Base Leg Aviation, has written books on maintenance and prebuy inspections, and posts videos weekly on his YouTube channel. He also volunteers as a Young Eagles pilot.