Light Piston Maintenance Texas Style

Back in June, I visited the Sikorsky Global Helicopter facility in Coatesville, PA. I was doing research for an article on its S-92 medium lift transport/utility helicopter. (That article is in the works for a HeliMx issue sometime next year.) If you have ever been up close to an S-92, it is an impressively-sized machine. While touring the Sikorsky facility, I saw that the S300C helicopter is also manufactured there. Now that is truly a difference to be seen. It was like looking  at a full-size hen and a baby chick.

I met Valerie Williamson of Denton, TX-based Longhorn Helicopters Inc. while attending the 2012 ALEA convention in Reno, NV. Longhorn Helicopters Inc. is located at the Denton Municipal Airport (KDTO), just 30 minutes north of Dallas-Fort Worth. It operates four low-time, well-maintained Sikorsky/Schweizer 300C training helicopters and one Bell 206 BIII Jet Ranger. I refer to the aircraft as a Sikorsky/Sch-weizer aircraft as, depending on who you are talking with, you might hear either name mentioned. Longhorn Helicopters offer flight training packages for private pilots through ATP certification, night-vision goggle training, aerial photography, pipeline/powerline surveillance, external load operations, charter and helicopter rentals. It has eight experienced flight instructors — and as with any helicopter, if it flies, it needs to be maintained.


Maintenance is something Longhorn Helicopters takes very seriously. The three A&P mechanics on staff keep the aircraft in their best condition. If a maintenance issue arises the aircraft is usually back flying the same day.

The Sikorsky/Schweizer 300C is probably familiar in appearance to most A&P mechanics in our industry, but if you are not familiar with it, here is its parentage, general specifications and performance data:

- It is considered a light/utility/trainer helicopter

-  It was first introduced in 1964 by Hughes Helicopters. In 1986, Schweizer acquired all rights to the helicopter from McDonnell Douglas, which had purchased Hughes Helicopters in 1984.

-  In August 2004, Sikorsky Aircraft Corp. purchased Schweizer.

General Specifications:

- Crew: one pilot

- Capacity: two to three passengers

- Payload: 950 pounds

- Length: 30 feet, 10 inches

- Rotor diameter: 26 feet, 10 inches

- Height: 8 feet, 9 inches (2.7 m)

- Disc area: 565 feet, 2 inches

- Empty weight: 1,100 pounds

- Loaded weight: 2,050 pounds

-  Maximum takeoff weight: 2,050 pounds

-  Powerplant: one Textron Lycoming HIO-360-D1A four-cylinder, horizontally-opposed, 190 hp (141 kW) engine Performance

- Maximum speed: 95 kts (109 mph)

- Cruise speed: 86 kts (99 mph)

- Range: 195 nm (204 miles)

- Rate of climb: 750 feet/minute


The following interview is with W. Reed Parsons, D.O.M. at Longhorn Helicopters Inc.

HeliMx– How would you describe your primary use of the S300C?

Reed– Our piston helicopters are almost entirely used for flight training. A very small percentage of the time they are used for photo flights, golf ball drops (a drawing or raffle accomplished using a helicopter to drop numbered balls above a target hole), sightseeing and Easter egg drops. Flight training can be subdivided into private, commercial, instrument, certified flight instructor (CFI), long line (external load), night-vision goggle (NVG) — yes, one of the 300Cs and one of the Jet Rangers have NVG lighting, and recurrent training. All but one of our 300Cs are instrument-capable trainers, though they are not certified to fly actual IFR. Maintaining instrument training piston helicopters is a little more of a challenge. Contact training maneuvers such as hover auto rotations, run-on landings and full down auto rotations are hard on gyros.

HeliMx– How many hours a year do they fly?

Reed– The 300Cs are each averaging around 100 hours per month. The Jet Rangers fly about half as much.

HeliMx– How many maintenance personnel do you have and what are their positions/titles?

Reed– Here at Longhorn there are four certified A&P mechanics and two of them have IAs. Dale Williamson is one of the IAs, but he wears many hats including designated pilot examiner (DPE), and he is one of the company owners. Dale is usually busy running things and only puts his mechanic clothes on once a month or so to pinch hit. Up until the end of July or beginning of August, we only had two full-time mechanics: Juan Pulido and myself. I am an IA and I am also director of maintenance. We do not have set titles for the other maintenance personnel. Juan and I seldom got a weekend off and we work overtime quite a bit, so we have now hired a third full-time mechanic.


There aren’t many mechanics with experience on the 300C, so I actually prefer to hire entry-level folks with an A&P who I can train in our methods. Juan was fresh out of A&P school a year ago, but he has learned quickly, is very conscientious and has taken on a lot of responsibility.

Dale Williamson is the owner, flight instructor and examiner, who has been an A&P I.A. for 20-plus years. Juan is an A&P with one year of experience, a “journeyman” Schweizer 300C mechanic. Eric McClain is a newly-hired A&P just out of school.


HeliMx– How does your operating environment affect your maintenance on the engine?

Reed– As to the climate, we have very hot summers here in North Texas, with many days over 100 degrees. Our winters are not too cold, and the heli-copters seem to have no problem operating in sub-freezing weather. We have little experience with temps below zero degrees. Windy days can happen year round. Heat is the main climate problem we face. We have to adjust the idle fuel mixtures in the heat of the summer to avoid running rich. After flights, the pilots must perform lengthy ground runs to properly cool the engine. This helps prevent coking the exhaust valves. These engines tend to burn more oil during those cool-down runs at lower rpm, compared to normal running rpm. This occasionally leads to a fouled sparkplug, but they almost always clean up on their own during warm up. Our mechanics check the idle mixture every time we do an engine run up. If the idle mixture can’t be adjusted properly, we send the fuel servo off to be adjusted and tested. This is often required even on new engines and sometimes indicates internal defects. We have never had an engine fail to make time between over-haul (TBO) 1,500 hours.

There are other environmental factors to consider also. For the cooling system to work well, it has to be clean. When hovering over loose grass, it sometimes gets sucked into the scroll fan and can restrict flow to the oil coolers. Therefore we clean the oil coolers often and check for trash. Dirt and grime also cause the same problem, so we are vigilant to get any oil leaks stopped and clean the engines. Our field elevation is 642 feet, so we have sufficient power to fly even when it is hot. However, on very hot days, some of our helicopters barely have enough power for max-performance takeoffs. For reasons unknown, we find that some helicopters are stronger than others. Even after engine swaps, the stronger ones are still strong and better lifters.

HeliMx– What engine work do you not perform in house and why?

Reed– We swap out cylinders if needed, 500-hour magneto inspections, change front crankshaft seals, change fuel pumps and we are now purchasing an engine core in order to overhaul our own engines. Of course, we will be sending many of the parts out for inspection/overhaul, so our main job will be reassembly. We find it to be very worthwhile to subscribe to the pubs, buy the tools and test stand to work on the magnetos. They need a lot of attention and it pays to open them often to check for problems and replace parts. Many people consider the magnetos to be throw away, but we find they make it to TBO just fine if well cared for. We do not overhaul components like cylinders, fuel injectors, etc. We send those out.

HeliMx– With regard to the S300C engine, what are the most common maintenance issues that you see?

Reed– Sticking exhaust valves (not very common, but very serious). Thanks to several of the things we do to prevent it, we seldom have problems with sticky valves. I suppose it is due to our hot climate, but sticking exhaust valves have been an issue in the past. Helicopter engines run at 100-percent rpm and the helicopter will not fly if an exhaust valve sticks. If the engine is immediately unloaded by lowering the collective, the valve usu-ally unsticks and power is restored. However, this doesn’t mean the problem is solved. The valves still must be inspected.

We find it good to be vigilant listeners for “morning sick-ness,” an intermittent hesitation or miss during warm up. We train the pilots to listen for it. It is a very distinctive type of misfire and easily identified. It may be the only warning before an actual exhaust valve sticking event in flight, so we ground the aircraft and follow the engine manufacturer’s instructions to fix the problem (Lycoming SL L197A, SB 388C, and SI 1425A). Select good engine oil that works well. When we first began operating these helicopters, we had more of a problem with sticky exhaust valves. After trying different oils we have found one that seems to work a little better. We accelerate the schedule for valve guide inspection (Lycoming SB 388C) and usually do it 100 hours early. This procedure takes one person about six hours including reaming valve guides that are coked up. Another common maintenance issue is dry tappet clearance of valves. While checking valve guides, it is also a good idea to check dry tappet clearance. On new engines we always do this during the first 200 hours. Push rods can be changed out to correct the clearance.

HeliMx– Any maintenance tips you want to share with our readers?

Reed– Here are a few:

-  Remove the magnetos often and inspect them internally per the manufacturer’s instructions.

-  Fix oil leaks. This should go without saying, but many people put up with oil leaks around the magnetos, push rod tubes, rocker box covers and oil-return lines. Oil at-tracts dirt which blocks oil coolers and clogs the screens on fuel injection nozzles. That, in turn, will affect fuel flow by preventing venting to the atmosphere.

-  Flow check and clean the fuel nozzles often. Bad fuel flow with rich or lean cylinders can contribute to valves sticking.

-  Inspect intake manifold induction tubes often for loose-ness and bad gaskets.

-  Change engine oil every 25 hours.

-  Check the oil-pickup screen for debris on the Lycoming engine, as well as the cut open oil filter.

-  Watch for chaffing around the oil lines. They will saw through a B-nut or a fuel line in short order.

-  Don’t let the ignition wires touch anything (for instance, in the upper engine area). They will vibrate and wear a hole through the insulation.

-  Inspecting security of the alternator mount is a 100-hour item that should taken very seriously. Shims are used in the alternator mount to facilitate adjusting belt alignment.

If not properly shimmed, the tightest of mounting hardware still cannot do its job and vibration will destroy the alternator mount bracket. There you have it, light piston engine maintenance, Texas style. If you are ever in the Denton area, stop by Longhorn Helicopters to say hi. I am sure Reed would love to show you his operation.

Reed Parsons has worked in many different fields so far in his lifetime. As a youth he broke and trained horses, as well as repaired farm equipment. After getting a degree in biomedical science from Texas A&M Univer-sity, he worked in various fields of medical research and even ran a children’s home. He received a fixed-wing private pilot’s license in 1995 and began working on aircraft under other A&Ps in the late 1990s. After gaining enough on-the-job experience working on all kinds of fixed-wing aircraft, he obtained his A&P license and an instrument rating. He began working on S300C helicopters in 2006 when he went to work for Longhorn Helicopters. Since then, he has received inspection authorization and his helicopter private pilot’s license.