SENTINEL OWNERS AND PILOTS ASSOCIATION

FREQUENTLY ASKED QUESTIONS ABOUT STINSON L-5's

Q. How many L-5's were made?

A. There were approximately 4,000 Sentinels built. The accepted figure is 3,790, but this only represents the total deliveries taken by the military from 1942 to 1945. The government actually had orders for 4,675 airplanes but the last 885 were cancelled. After the war an unknown quantity of Sentinels were assembled and sold surplus through the War Services Administration from the stock of left over airframes and parts. An independent firm, called the Sentinel Aircraft Company, was set up in late 1945 and continued to provide parts and support to the military into the 1950's. It is not likely that they manufactured any aircraft.

Q. How many Sentinels are there now?

A. There are around 300 L-5's listed on the world's civil airplane registers, although there are probably many more restoration projects and derelicts that are not registered. Very few of the L-5's sent overseas during WWII were brought back. Most of those that were not badly damaged or destroyed were given to foreign governments to help rebuild their devastated air forces. About 250 Sentinels are registered in the United States but less than half of them are in flying condition. The CAF operates eleven L-5's that can often be seen at airshows during the summer. Another dozen or so airplanes reside in museums, including the first production airplane which is displayed at the National Air and Space Museum. The club maintains an up-to-date database of all known L-5's.

Q. How much does an L-5 cost?

A. In 1944, the average cost of an L-5 was about $9,500. Adjusting for inflation, that is approximately equivalent to $120,000 in 2008 currency. Today, they run from $7,500 for a "basket case" project to over $75,000 for an example restored to museum quality. The average price for a flyable Sentinel that is currently licensed, annualed, and in good repair is around $45,000.

Q. How expensive are they to operate and maintain?

A. The L-5 burns about 11 - 12 gph in cruise and almost twice that much at take-off power. A one-way trip of 100 miles (no wind) costs about $50-$60 at average fuel prices. There is an auto-gas STC available that can cut this by about 20%.

An L-5 costs about the same to maintain and insure as other tube-and-fabric "taildraggers", but O-435 parts are becoming scarcer all the time so costs are bound to rise. A set of main bearings, for instance, currently costs between $800 and $1,000. A "top" overhaul with new rings and pistons averages $6,000. A complete rebuild can cost from $9,000 for a "field tolerance" overhaul to more than $20,000 for a "factory tolerance" job including rebuilt accessories - if you can find someone to do it. There is no legal alternative to the Lycoming O-435 in the U.S. at this time, although in Italy they have approved a 230hp Lycoming O-540 conversion.

There is also an AD on some of the controllable propellers used on L-5's. This AD can cost up to $1,500 bi-annually to comply with. The fixed-pitch wooden prop isn't as efficient, but it has no AD's and is much cheaper to maintain. Fortunately, the L-5 has no other expensive AD's to worry about.

Q. Are L-5's aerobatic?

A. L-5's are not on the FAA list of "approved" aerobatic aircraft, but they are capable of all maneuvers except outside loops and inverted spins. They are stressed for +10.2 and -4.3 g's, but they do not have inverted fuel or oil systems so cannot fly upside-down for long. Due to their age however, "stunts" are not recommended unless the wooden wings and empennage are completely rebuilt and all critical fittings and hardware have been x-rayed or magnafluxed for cracks. There is no limit to the life of a well-maintained wooden aircraft structure, but glue joints can weaken over time.

Q. What other names or designations were used for L-5's?

A. The L-5 was originally designated O-62. The "O" stood for "Observation", but early in 1942 the "Liaison" designation was applied. All L-5's were officially called "Sentinels" but they were also popularly known in the field as "Flying Jeeps" or "Grasshoppers". The Navy and Marines used the OY-1 or OY-2 designation for 12-volt and 24-volt models respectively, and the Coast Guard used OY-1G or OY-2G to the same ends (the 'G' signifying a non-combatant search-and-rescue Coast Guard aircraft). The British used "Sentinel I" and "Sentinel II" to distinguish the observer model from the ambulance. In the 1960's, the U.S. Air Force re-designated the two basic Sentinel models as U-19 and U-19B.