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Greg Morris is the Chief Pilot of Gauntlet Warbirds, a warbird and aerobatic school outside of Chicago. They operate a Decathlon, Extra 300, T-6, L-29 and L-39, and he reviewed Lotus' FSX L-39 v1.3 comparing it with his own experience of flying the real thing.
Contrary to what many air show crowds tell me the L-39 isn’t an A-4 or an F-5. The L-39 is one of the most popular and successful jet trainers ever built, with design beginning in 1966 and production of advanced variants continuing today. Almost every fighter pilot in the former Warsaw Pact trained on the L-39 and it serves today with many third world air forces as a frontline ground attack aircraft.
Its combination of attractive lines, relatively low operating expenses, good handling qualities and the availability of extensive parts and maintenance support in the west have led to the L-39 becoming the most popular jet warbird in the world with around 300 aircraft in the US alone.
The L-39 is an outstanding first jet for new student to fly, and transitioning them into the aircraft is relatively painless if they have some aerobatic experience. For students without prior jet time the most difficult aspects of learning to fly a real L-39 are learning the systems and controlling your energy, especially while doing aerobatics or in the pattern. Lotus Simulations’ L-39 add-on for FSX wonderfully captures these challenges and the joy of flying the jet.
For some context let’s walk through a typical L-39 flight. After your preflight is complete and you are strapped into the jet take a quick look around. The layout of the cockpit is extremely logical, with switches grouped according to their function. The two strangest things to a western pilot’s eyes are the push button flap controls next to your left leg and the large handle attached to the base of the stick. Aero Vodochody introduced push button actuated flaps and gear on their L-29, the predecessor to the L-39, but abandoned the button actuated gear in favor of a more traditional lever in the L-39.
The flaps however remained which requires pilots to glance at them to ensure they are selecting the appropriate position. The handle on the stick is pure Eastern Bloc, the L-39 has no nosewheel steering, it castors freely. To steer on the ground the rudder is defected and the brake handle on the stick applied, resulting in an unequal application of brakes and a turn. Students tend to apply the brake first and then attempt to position the rudder, resulting in at best a jerky turn and worn out brakes, and at worst coming to an abrupt stop on the taxiway.
The best technique to steer is to apply the rudder fully in the direction of the desired turn, and then gently squeeze the handle to control the radius of the turn. When you have 30-45 degrees of turn left release the brake and add a touch of power to help straighten out the jet.
With taxiing thoroughly briefed let’s start the jet. Lotus includes an excellent set of checklists with their L-39 package; however there are a few differences with their checklists and the flight manual. One example is the start procedure; Lotus has the throttle in the IDLE position before the engine is started while in the jet the throttle is set to the STOP position until either five seconds after the engine start sequence begins or 18% N1 (based on pilot technique and preference).
The L-39 is started with a small APU called a Saphire, which is mounted in the fuselage aft of the wing. It is started before the engine with a small button on the left control shelf, and once a light on the C&W panel illuminates indicating it is up to speed, it routes its exhaust through the engine to spin it up when the ENGINE START button is depressed
Five seconds later the throttle is placed in the IDLE position. All the pilot has to do from that point on is monitor the start sequence, primarily checking that oil pressure and N2 rise appropriately, the Saphire shuts off automatically, and that N1 stabilizes at idle RPM. Once the engine is started turn on all the remaining systems, seal the canopies, turn on the AC (my favorite step in the summer), check your hydraulic users including the flaps and speedbrake, and you are ready to taxi.
The L-39 is taken off with half flaps and unless the runway is very long power is brought up to full with the brakes on to allow the engine to spool. From idle to max power (about 106.7% N1) the L-39 takes between 12 and 14 seconds to spool up, so in the pattern N1 must be kept above 70% to ensure that the engine is responsive. To compound the problem the thrust curve on the L-39, like most jets, is nonlinear.
By reducing RPM from max to 99% N1 about 25% of the thrust of the jet goes away. Line the jet up with the runway trying to keep the nosewheel as straight as possible, especially on short runways as any steering at low speed has to be accomplished with brakes, resulting in an increased takeoff roll. Hold the brakes and run the throttle to max power, once N1 has stabilized and all the gages are good release the brakes.
The jet rotates at about 90 knots (all speeds depend on weight, I will use typical numbers for this review) and flies off at about 110 knots. Lotus’ aircraft all use KPH for their airspeed, the conversion is .54:1.
When established in a positive climb retract the gear and at 140 knots bring the flaps up. Allow the jet to accelerate to a minimum of 165 knots and then turn out of the pattern for the practice area. Allow the jet to continue to accelerate to 200 knots (Vy at max power is 216 but airspace often limits you to 200). Some pilots like to reduce power to 103% at this point while others maintain 106.7% until they are at altitude. Either way climb to the mid-teens for some maneuvers.
front and rear cockpits - both are fully functional
In the climb the jet’s systems need little if any attention aside from standard monitoring. The ECS system automatically regulates the differential pressure in the cockpit according to a preset schedule, a small dial at the lower right of the panel shows you cabin altitude in thousand of meters and differential pressure in kg/cm2 or atmospheres. Upon leveling off at 14,500’ throttle back to 99% for high cruise and some light aerobatics.
The L-39 is an excellent aerobatic platform with a good roll rate and adequate power for most military style aerobatics. To setup for an aileron roll allow the jet to accelerate to at least 250 knots and pitch up ten degrees, then apply full left stick and watch the world go around. Loops and over the top maneuvers are entered at 320 KIAS and 103% power and are entirely conventional. The most common student error I see in loops is that pilots have a tendency to add back pressure to the stick while coming down the back side of the maneuver, resulting in an accelerated stall when the jet is vertical down.
Stalls in the L-39 are a joy, the engine is automatically controlled by a mechanical fuel control unit so you can position the throttle anywhere between the idle and max power settings and it won’t overtemp or flameout no matter how fast you move it. This is not typical for jets of the era where aggressive throttle movements could result in flameouts or damaged engines. To setup for a power off stall simply pull the throttle to idle and increase angle of attack to maintain altitude as the jet slows.
The L-39 has a very distinct buffet before the stall, if you ignore that and continue to apply back pressure it will exceed critical angle of attack and depart. The L-39 has a very benign stall, it will begin to descend and might drop a wing slightly, however this can easily be corrected with some rudder to pick the wing up. A gentle relaxation of back pressure followed by selecting max power will fly the jet out of the stall nearly effortlessly.
After some fun in the area it is time to reenter the pattern. The preferred way to enter the pattern in the L-39 is with a military style overhead break approach. Initial is 2-3 miles from the runway at 1,500’ and either 200 or 250 knots, depending on airspace restriction. At the break (either approach end or mid-field) reduce power to 70%, extend the speed brakes and roll into a 180 degree turn at 60 degrees of bank, maintaining altitude.
The required 2G pull will bleed energy to get you down to gear speed of 180 KIAS. Below 160 you can extend flaps, some pilots like to extend the flaps in increments while others select full down once on speed. Once the flaps are down increase power to 80-85%, pitch for 140 knots and start a 180 degree turn to final. After approximately 90 degrees of turn you will intercept your desired glideslope, increase power slightly to maintain it and once on final slow to 120 knots. At about 50 feet AGL start reducing power to idle and at five feet flare the jet gently.
After touchdown hold the nose up as long as possible to use aerodynamic braking to slow down, then lower it to the runway and apply full forward stick to make sure that weight on wheels switch engages (without it the system prevents any brake pressure from being applied).
Lotus' L-39 does an incredible job recreating the jet down to minute details, even modeling many system failures and warning accurately. I would love to write a detailed breakdown of how the sim differs from the jet here, but I can't. I flew the Lotus L-39 through all of the standard training profiles and even my air show routine and I performed as well as any simulator could. The profiles that work in the real jet work in the sim, as do the procedures.
I have started recommending Lotus' software package to all my students as a useful way to practice the checklists and procedures without having to pay to run the engine. After all, FSX and the L-39 add-on cost about the same as three minutes of flying in a real L-39.
-Greg Morris is the Chief Pilot of Gauntlet Warbirds, a warbird and aerobatic school outside of Chicago. They operate a Decathlon, Extra 300, T-6, L-29 and L-39.
Ironhand's Kauai and Niihau installed , Aerosoft Dillingham, FS Genesis HAWAII PRO MESH FSD-125 , REX, FEX, ASA and Lotus L-39C v1.3 for FSX were used in this article,
ENB Mod used @ 1600x1200, AA x16, AF x4 - FSX-A set at high settings. FPS locked at 30 FPS.
Screenshots were taken by ThomasDWeiss on an Intel DX58SO, Intel Core i7 920 Quad Core 2.66GHz, 4 GB 1333 RAM (CORSAIR XMS3 2x2GB PC3-10600 1333MHz), 2x500GB RAID 0, WinXP Pro, Nvidia GeForce GTX285 1 GB - and were not edited in any way other than resizing. As always, we do not profit from any sales of anything we review.
to go to Lotus web site , click on the image bellow - it will take you there...
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Posted on Friday, December 11 @ 18:20:00 PST by Greg_Morris
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Average Score: 4.66
Votes: 24
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