Van's Air Force
Western Canada Wing
|
Van's Air Force
Western Canada Wing |
After getting out of the air force,
in 1945, I became a part owner in a small charter and flying school operation,
and continued to be involved in commercial aviation until retirement.
With the switch from the airforce paying the bills to me paying them I
really got interested in how my engines were being handled. It didn’t
take long to see the difference in costs between an engine that was carefully
handled and one that was handled by an inexperienced pilot or hot rodder.
My priorities have always been safety first and costs second, and over the years it became very plain that the best and cheapest way to accomplish this was to start out with a new engine or a premium overhaul and don’t cut corner’s under the cowlings. After a few years I finally settled on the following procedures and found them to do the best job.
These are the power settings and handling
procedures I have used on the Lycoming O-540, O-360, and O-320 engines
over the past thirty years or so. I have found them to give the best
combination of long life, speed versus fuel consumption, and, most importantly,
no engine failures. All of my life my engine handling priorities
have been:
1. Do the best you can to prevent an engine failure.In my opinion, “engine handling” begins when you first decide to start the engine. So these are the rules I have followed.2. Keep engine operating cost as low as possible by having every engine run its full time between overhauls.
3. Avoid propeller damage during ground running, and try to cause the leased amount of disturbance to others from noise and prop wash.
4. Make maximum performance a consideration only when conditions warrant it.
1. Never attempt a start below freezing without pre-heating. Learn how much prime is required under various conditions to start in, say, three or four blades. Never prime with the throttle.All of the above RPMs pertain to a constant-speed prop, which will be turning 2700 RPM in full-fine for take-off. I have no experience with a fixed-pitch on an RV but, in talking to others, procedures should be the same. The difference would be (in the case of the new Sensenich prop for the O-360, for example) that the RPM at the start of take-off would be somewhere around 2200-2300, increasing with airspeed until reaching around 2700 in level flight at critical altitude. I believe, for the good of the engine, it should never be operated over 2500 RPM continuously which, with the Sensenich prop, would mean reducing the manifold pressure to around 20 inches.2. Keep engine RPM to 1000-1200 for a few minutes, monitoring oil pressure. Keep under the red line. You may have to drop below 1000 RPM initially, if the engine is started close to freezing with heavy oil, to keep oil pressure within limits.
3. Move to the run up area and, assuming one is on pavement, warm up into wind at 1400 RPM, to 100-120 degrees oil temperature.
4. Check the mags (or electronic ignition) at 1700 RPM. In the case of a constant-speed prop, exercise the prop a couple of times with a 300-400 RPM drop. I don’t go above 1700 for a mag check, unless something shows up, for the good of the prop. Going into grass or gravel strips, if I have any concerns about prop damage, I will check the mags in the circuit before landing and then just check for a dead one prior to take off.
5. Take off at full throttle and, in the case of the RV, climb out at say 110-120 indicated. As soon as comfortable, throttle back to 24-25 inches of manifold pressure and, in the case of a constant speed prop, reduce to 2400-2500 RPM. I have always made it a rule to keep full throttle operation to one minute, maximum, unless circumstances dictate otherwise.
6. Continue climb-out at these settings until reaching desired altitude, starting to lean at 3500-4000 feet, and keeping well on the rich side of peak. On reaching cruising altitude, level off and cruise at 2400 and 21-22 inches manifold pressure for say 5 minutes, to stabilize temperatures. Then lean to peak on the hottest cylinder, less 50 degrees on the rich side.
7. Plan your decent to maintain 400-500 FPM at say 18-20 inches manifold pressure, gradually reducing to say 14 inches on arriving at circuit height. This cools the engine gradually (prevents shock cooling). On levelling out in the vicinity of the airport, you can reduce power as appropriate to maintain the speed you desire. The speed is now low enough now that this power setting will keep the engine temperature okay. Another reason for restricting descents to 500 FPM is for passenger comfort. I have found that people who don’t fly very often have sensitive ears, especially if one has been at a high altitude for an extended period. This means that if you have to let down 7000 feet you have to start the let down in a RV roughly 45-50 miles back. Using this method assures the proper control of engine temperatures and also allows for immediate shut down of the engine after landing.
The Lycoming manual says not to operate at over 75% continuously. This equates to around 2400 RPM and 24 inches. The recommended TBO is 2000 hours, and this can be achieved if the aircraft is flown on a regular basis (at least every two weeks) and cruised at 65% power. This has worked for me. I have never had to change a cylinder on a Lyc, all have run their full time, and I’ve never had one quit except for fuel starvation.
Using these settings I ran nine light twins with O-540s and IO-540s for several years, each one flying 1000-1100 hours a year, without a single cylinder change and with every engine reaching it’s recommended TBO.
Restricting RPM on the ground to 1000 or so will keep prop damage to a minimum.
Really, what all this boils down to is
to use 75% for climb and as close to 65% for cruise as you can get.
The rest is just common sense.
One need not feel restricted by these
procedures. If you need it, use it. The small Lycs are famous
for their reliability, but every time one strays from the above it takes
a bit away from safety and increases the costs.
Here are a couple of items I have picked up over the years as to the maintaining and handling of Lycomings. While we are talking about Lycomings in particular, these observations would apply to most naturally-aspirated, opposed engines that I have had experience with.
A member of the Web Standards Project |
Support free speech. |
Built on...
...FreeBSD |
|
|
Van's Air Force Western Canada Wing is not affiliated in any way with Van's Aircraft Incorporated. Western Canada RVator is not a publication of Van's Aircraft or any other corporation. All products reviewed or mentioned are not necessarily recommended for use by RV builders, but are described for information only. All builder's tips are presented only as a source of information and a forum for exchange and the sharing of ideas and construction methods. No responsibility is assumed, expressed, or implied as to the suitability, accuracy, safety, or approval thereof. Any party using the suggestions, ideas, or examples does so at his or her own risk and discretion and without recourse against anyone. The members of Van's Air Force Western Canada Wing, the editor of the Western Canada RVator, and all authors and contributors are not responsible for any product or builder's tips misuse, incorrect construction, or design failure, nor any other peril. All material on this web site is copyright Van's Air Force Western Canada Wing, or copyright the attributed author, unless otherwise noted. | |||