Flying the L39

 

Iíve been meaning to write this article for a while, but gosh, itís a huge topic.I could write an entire book about maintaining and flying the L39.I will try hard to keep it concise.

 

The L39 is a Czech-designed and Czech-built tandem two-seat dual-control jet trainer, used by the Russians, Ukraine, and just about anyone else in the ďeast blocĒ.Kids learn to fly it, then move on to Sukhois and MiGs.

 

You can buy one for less than a Cirrus.Yes, it will burn a bit of Jet-A but itís really not that hard to fly, and itís easy to maintain.Anyone that tells you that you have to be a Hero in the league of Chuck Yeager to fly a jet is a blowhard full of bullshit, and boy are there ever a lot of them in aviation.Jets are so much easier to fly than piston/prop aircraft.So much less to worry about.Just make sure you get Prist in your fuel.

 

Itís a little weird, compared to western stuff, with itís metric hardware and Nitrogen, but itís actually very easy to maintain and fly, reflecting the Russian attitude towards high-volume production.The fleet has over FOUR MILLION hours on it, and there are over 200 L39ís privately flown in the USA.I think there are five now in Canada, and we fly two of them.

 

We fly two L39C models Ė the trainers.There are also ZO and ZA models, which are more intended as working airplanes with more hard points.

 

 

Preflight

First thing you look at is the 24V battery in the nose.We normally disconnect the battery when the aircraft is not used because there is a constant drain (fire loop) which will kill the best battery in a couple of days.Itís a good idea to charge the battery up before you fly the L39.I like the G7200 charger at Canadian Tire.Be sure to button up the nose cover securely with a large slot screwdriver, after you reconnect the battery.

 

While youíre at the nose, check the nitrogen pressure.You have to have a 3000 psi N2 tank in the hangar if youíre going to fly an L39.You want 50 Ė 150 kg/cm^2 indicated on the external gauge on the left side of the nose.It is mostly used for the canopy seal and will use a little bit each time you fly it.

 

We donít bother with the oxygen system, at the altitudes we normally fly the L39.It has 9,000 feet of cabin pressurization differential which is all you need below 18,000 feet.

 

At the nose, check the nose tire inflation and oleo strut.Also check the main tire pressure and oleos.I like 100 psi in the mains.

 

Remove all the intake and exhaust and pitot plugs and covers.While youíre at the tailpipe, take a powerful flashlight and shine it up and check the oil level in the SAFIR turbine starter (kinda-APU).Make sure itís at least 50% full.It uses an ounce or so, every time you start it.

 

I might suggest you fill up the main tanks and the tip tanks.I like to see 800 kg of fuel indicated when I take off.That time gives me options.It burns 70 gph just at 56% idle, over 300 gph on takeoff, and around 140 gph in slow, low-power cruise.When it burns down to around 650 kg or so, the tip tanks automatically sequence into the mains.

 

Check the hydraulic fluid level on the left side, and the engine oil on the right.If the engine oil on the right shows no oil, donít panic.Sometimes it drains to the bottom of the engine.What you can do in this situation is start the engine briefly, shut it down, then check the engine oil level again.Itís best to check it after you fly, actually.Itís a newbie mistake to pour excess engine oil in, when it runs to the bottom.That will totally overfill it.

 

When you think itís ready to go, climb in the front seat and flip the battery switch on, and also the engine/fuel pump.Check the voltmeter.If you donít have at least 22 volts DC, you canít get a start on the internal battery.

 

If the battery is weak, and you have an external source of 24V (two truck batteries in series works well) with a 24V Cessna external power plug, you can start it that way.The connector is on the left side, behind the wing.

 

 

Start

 

When the aircraft is ready to go, climb in.Be sure and raise the hinged step!There are two kickplates to help you climb in.Stick forward as required to hook up the parachute belts to the center clip.The parachute is connected to the seat, which on ours are cold Ė no pyros.

 

Canopy down and locked, using the red handle on the left side all the way forward.

 

On the left side, emerg/parking brake red handle all the way forward.

 

The throttle has a thumb switch aft.Press it to pull the throttle back to cut the fuel off, past idle stop.

 

Battery switch on, engine/fuel pump switch on.Confirm 22 volts minimum.Select SAFIR start (or however it is labeled).It will wind up to 80% for a moment for a self-check, then if the oil and volts are good, it will wind up to 100%.Sometimes it will pee a little Jet-A on the ground.

 

Now, the yellow ďTURBINE STARTERĒ light is illuminated on the panel on the right side.Press the TURBINE start switch, and watch the N1 wind up to 25%.The N2 will come up to 5%.When it stabilizes, click the throttle forward to idle to supply fuel, and watch the EGT on the right side of the panel.

 

A good start will be below 400C.Sometimes it will go higher than that.If itís over the redline, press your thumb and pull the throttle past the detent to shut the fuel off.Get out and figure out whatís wrong.

 

A normal start will see the N1 wind up to around 56%, which is flight idle.Check the oil pressure, which should be around 3 kg/cm^2.Fuel pressure wonít read anything at idle.

 

Now select GEN on, INV 1 and INV 2 on, RADIO master on, and any other electrics you need.Every aircraft is configured slightly differently.Get the intercom going so you can talk to the guy in the back seat.Get the COMM radio on for freq and volume.

 

Slide the ECS lever knob on the right side all the way forward.At the center position, it will inflate the canopy seals, and all the way forward, the ECS will heat or cool.Put it on AUTO Ė not manual.

 

At this point, I select flaps takeoff (blender button one) and speed brakes in (forward) and trims neutral, getting configured for takeoff.

 

Pull the brake lever on the stick and make sure you feel some resistance and see both needles swing up on the gauges below.Release the parking brake by pulling the red handle to the center.

 

There are no toe brakes.Itís going to take some practice before you can taxi an L39 straight.

 

Taxi out and line up on the runway numbers for takeoff.

 

 

Takeoff

 

Pre-takeoff checks are simple.No warning lights, canopy locked, flaps set for takeoff, speed brakes in (forward), trims neutral.At least -5C oil temp.

 

Brakes on with the stick lever.Full throttle.I want minimum 105% N1, better is 106.8%.

 

Release the brake, you start moving forward.Try to stay off the brakes to stay straight.

 

Airspeed alive, around 100 knots you can rotate, and you will soon be flying.

 

At 120 knots, positive rate of climb, gear up Ė lever on the left.

 

Through 140 knots, flaps up.Lower the nose just a smidgen as required to avoid that sinking feeling.

 

Looking for 160 knots for obstacle clearance.We are on the back side of the power curve.

 

Over the obstacles, 190 knots, and the VSI will surge upwards.The airplane is happy when clean over 180 knots.Throttle back to N1 103% in the climb, and be prepared to turn immediately with more bank than you are used to because of the higher speed.

 

 

Cruise

 

Climb up to your desired altitude and back the N1 to the low 90ís when you level off, to try to keep it under 250 knots indicated.

 

Itís a very easy airplane to fly.Aerobatics are simple, smooth and slow.You can actually tailslide it, which will blow the mind of any western jet pilot.Only the billion-dollar F-22 can tailslide without a compressor stall.L39 is extremely resistant to compressor stall.

 

 

Descent

 

Remember, below 10,000 feet youíre supposed to keep it under 250 knots indicated, which is easy to blow through.It likes 400 knots indicated.You have speed brakes (boards on the belly) controlled by your left thumb on the throttle.Very handy to get the gear speed.I donít use them for the approach and landing, though.

 

 

Approach

 

An overhead break works well.Pattern (circuit) altitude is normally 1500AGL.For the downwind, I set N1 85%.At mid-downwind, gear down at 180 knots, then at 160 knots first stage of flaps (takeoff).Turn base, descend, looking for around 150 knots, no slower than 140 knots.Turn final, select full flap.Be patient and let the speed come down to 125 knots on short final with the throttle still set at 85% N1 or thereabouts.

 

Try really hard not to be a throttle jockey.Watch the trend of the airspeed closely, especially at low altitude.

 

 

Landing

 

Just before the runway threshold, throttle to idle, just like a Piper Cub.Flare and get the nose on the ground ASAP to activate the WOW switch on the nose which allows you to use brakes.

 

There is anti-skid to protect the tires, but try not to panic and lock them up.As you slow down, you can use more and more braking as you get weight on the tires.Stay straight on the rollout with your feet.

 

Taxiing in, I get the flaps up.Park it and put the brake on Ė red handle forward.

 

 

Shutdown

 

Reverse of what you did at start.Radio, Inverters, Generator off, throttle all the way back with the thumb switch to cut the fuel off.Engine/fuel pump and battery switches off.ECS lever back to unseal canopy.

 

Canopy lever back, rotate right and open.Flip the cover on the belt latch on your chest to release the belts, and climb out.After a while, you will learn where the kickplates are.

 

Fun, huh?

 

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acboyd@gmail.com

Nov 2014