Into the past , gliders relatively slow of the late 30s until the 60s were towed by planes equally suitable for slow flight .
- SV4 Stamp,
- the Tiger Moth,
- Fieseler Storch 156
Although initially not designed for this mission these all have the advantage of sharing a good part of their flight envelope (speed) with their contemporary gliders.
It is important to note that the designers of these planes had smartly chosen slow and “torquey” engines and high diameter propellers well suited to the slow flight ; making it all uniform and yet effective for the Towing Mission .
This is particularly true for the MS317 (below) and the Fieseler Stroch (then Morane 500 with a radial engine, below); the power plant of the Tiger Moth with its smaller propeller was not very suited to this work and did not procure a good climbing speed to the attelage.
Later in the late 60s and during the 70s, when all this material became too old and too expensive in maintenance and use, the need to find a replacing of these venerable planes appears.
Gliding searched therefore classically in the aircraft “modern” park the future elect capable of carrying out this task.
During this period stood on the French market a few Robins DR400, Jodel Mousquetaire and Morane-Saulnier 893E Rallye all come from a single need:
travel with family over 200 km / h without an exessive consuming !
Excluding this transport task, these aircrafts have something else in common, they use the same engine, a Lycoming O-360 180HP and its approved propeller of an imposed diameter.
Lycoming and Continental engines are almost the only aircraft engines to successfully survive the WW2 aftermath. Understand that the extreme technical knowledge that was the heyday of light aviation 30s-40s was completely swept by the emergence of the “jet” commercial aviation of the end of World War II. Thus almost all radial and V engines produced by the aviation industry was stopped in favor of single flux turbofan engines and turboprop commercial aircraft.
Technically speaking, the years 60s-70s have seen the emergence of the very first plastic gliders and loss last tow planes with radial engine and large propeller with the exeption of PZL Wilga.
In terms of Towing, the glider generational shift (wood and fabric to plastic) does not fundamentally change things, fifteen or twenty kilometers per hour more in towing. By contrast, changing tow plane generation is more radical if we stick to the usable speed range with the new aircraft (Rally DR400 or Mousquetaire, Cessna L19). p>
So we found himself in a situation where we had to tow a slightly higher speed than before but with aircraft that are no longer does for slow fly and, more importantly, have small propellers and higher engine rotation speed.
Today we are in a situation almost identical to that of 60s-70s. The older planes (certified with O-360) have excessive operating costs for clubs and they must be replaced . There still does not exist certified aircraft fully and smartly designed for this mission.
The answer once more is given more or less successful adaptation of contemporary Tourism plane .
New fact, since there is so to speak further certified general aviation in Europe, the French legislation was recently constraint to allow towing gliders (certified gliders) by microlight planes ( no certification ), which results in a lower operating costs (which is beneficial for clubs) but also performance restriction at a level of course meets regulatory requirements but still insufficient to ensure strong initial slope during takeoff especially with modern two-seater gliders ( no evolution at this level following the changing of tow plane generation).
Two “home made” attempted solutions (CNRA = certified) appeared during the last 20 years without making any notable upheaval in terms of vertical speed:
Witnesses to the desire to change things, gliding world will provide an effective solution to this problem, both machines have been begotten. It includes a small increase in climb performance but unfortunately the conservation of major Rallye’s defects (Heavy motor and small propeller, use of 100LL) will have been preserved which explains why the lack of performance gap and the lack of enthusiasm for these last. Adding that they are more expensive than microlight aircraft and hard to produce.
Whatever the current machines, average performance (certified tow plane or microlight) are about:
- + 2.5 m / s to a single-seat glider towed.
- + 1.5 m / s to a 2-seat glider towed.
It is possible to make much better by designing a plane from A to Z and not modifying an existing aircraft from its initial mission. This is the mission that is given itself PSX-Aviation in the “Nout” project.