Hi everyone
I just got a new L39CT. on it's way to US from Germany, can anyone advice me regarding to upgrade to Garmin G500 with GNT 750 or somthing else, my budget is $40 000 max.
please email me to affes@msn.com or call me at 201 481 0010

regards

Vatche

Statistics: Posted by Vatche Aghjayan — May 17th, 2012, 6:46 am

Guys,
We are getting more busy every day. We have expanding operations on three continents. If there is an experienced technician or two looking for a new opportunity, then please contact me offline. We are doing new, exciting things !!!

Regards

Richard Hess
President
International Jets
Hess737@aol.com
C 404-964-4885

Statistics: Posted by Richard Hess — May 16th, 2012, 4:53 pm

Hi guys, interesting responses being posted, reminds me of the old days ......we need to get the forum activated again as there is voluminous information available out there if all the old guys will just discuss it. Bret asked for a response .....so here it is. I have a stock L-39C and am very conservative on fuel as my posterior cannot take much over 90 minutes on those Czech seats. If not worried about stretching the range I usually stay VFR at 17,500 or 16,500, as I do not have an autopilot and am afraid of an altitude bust in the flight levels, 200 feet deviations can happen quickly. If I need to go high then I have gone to 25,000 and kept it at 98%....I did this for weather going to Reno .......I always try to stay high in close and then even cancel IFR if not a busy area so that I can make a steep VFR descent. My longest leg ever was 500 miles and I went high. A conservative and easy timer (I do not have a fuel flow) is to use the numbers on the fuel gauge as minutes instead of quantitiy. In other words the 4 is approximately 40 minutes left at cruise.....I always land with a little more fuel than indicated by this method, but at least it is more than I needed and not less. As far as numbers published in the manuals, I find them optimistic and I seem to burn more than they do, guess they have the same writers as Cessna and Beech. Darryl

Statistics: Posted by Darryl Christen — May 14th, 2012, 3:51 pm

Is saving 1/10th of an hour done for the purposes of "hourly cost" on the aircraft? In fact,... not counting fuel... what do most of y'all consider the "hourly cost" for an L-39?

Notwithstanding saving 1/10th of an hour, I'm pretty sure your greatest "nautical miles per pound" will occur if you plan your descent in idle, and at L/Dmax. In the T-38, we compromise by using our cruise mach (~310 KIAS) versus L/Dmax (240 KIAS) in the descent to keep the speed up,... and it does not appreciably affect our fuel burn. We just have to start down a little later, since it is 7 deg nose nose, vice 5 degrees.

Also, we plan everything based on pitch. VVI is too erratic (we have a lag on our VVI), and not a "control" instrument like the attitude indicator (ADI). It's easier to fly a specific pitch on the ADI in IMC conditions, rather than constantly modifying your pitch to obtain a certain VVI... "control-and-performance" basics.
And the math is easier, which works well for me since I"m more of a knuckle-dragging Neanderthal when it comes to working math on the fly. I need to lose 21000' using 7 deg nose low... divide 210 by 7 = 30 nm for the descent.

Statistics: Posted by Jon Huggins — May 13th, 2012, 9:49 am

Is saving 1/10th of an hour done for the purposes of "hourly cost" on the aircraft? In fact,... not counting fuel... what do most of y'all consider the "hourly cost" for an L-39?

Notwithstanding saving 1/10th of an hour, I'm pretty sure your greatest "nautical miles per pound" will occur if you plan your descent in idle, and at L/Dmax. In the T-38, we compromise by using our cruise mach (~310 KIAS) versus L/Dmax (240 KIAS) in the descent to keep the speed up,... and it does not appreciably affect our fuel burn. We just have to start down a little later, since it is 7 deg nose nose, vice 5 degrees.

Also, we plan everything based on pitch. With your TAS changing in the descent, the VVI would move around too much. Plus it's easier to fly a specific pitch on the ADI in IMC conditions, rather than constantly modifying your pitch to obtain a certain VVI... "control-and-performance" basics.
And the math is easier, which works well for me since I"m more of a knuckle-dragging Neanderthal when it comes to working math on the fly. I need to lose 21000' using 7 deg nose low... divide 210 by 7 = 30 nm for the descent.

Statistics: Posted by Jon Huggins — May 13th, 2012, 9:46 am

Guys,
Here's some further shortcut planning from me. At most altitudes, your idle fuel flow is about half what it is at cruise. You only descend for about 2-4 tenths of an hour. So, total descent burn is 15-25 gallons depending on altitude, descent rate, and power setting. Idle is the most efficient but it slows the aircraft down unless you plan for 2000 fpm or more. Personally, I like to keep the power up around 90-93% initially in the descent. My true airspeed increases about 0.1 Mach and fuel flow is a little lower than at cruise until low teens. Then get it back to 80% or lower approaching 10K to reduce to 250 KIAS. I plan for 1500-2000 fpm. The trade off is just a few gallons but it also knocks a good tenth of an hour off your flight time.

I'll bet other jet Warbirds have similar relationships to idle vs cruise power settings. Also, if you want to maximize your range you need to carefully look at altitude and speed profile. The L-39 optimum altitude is about FL270 clean. The T-33, and the A-10 coincidentally, are more like FL350. RVSM gets in the way of efficient operation and can cause a 40% reduction in range!

Most fighter/trainers require the use of oxygen at optimum altitudes due to cabin pressure. Do you guys keep your oxygen system operational for this requirement, or in case of a loss of cabin pressure or smoke in the cockpit? I've seen many who do not, or those who seem uncomfortable using the system. Just a couple of minutes of supplemental oxygen after an hour or two at a cabin of 12,500 ft makes an amazing difference in how you feel.

Hope this helps. I guess I've been forced to find ways to optimize L-39 range since I've ferried four to Europe over the last two years with more to follow. My longest leg with normal fuel (343 gallons) was 657 nm (60 knot tailwind), and 713 nm with 463 gallons on my first North Atlantic ferry with a little headwind. Not bad...

Cheers

Rich

Statistics: Posted by Richard Hess — May 13th, 2012, 4:36 am

Amos,
Thanks for that info. I hadn't flown the L-39 in a couple of years (was never checked out), and had forgotten there was a TAS needle.
Looks like 5 degrees nose low is the pitch picture you're describing for the idle descents.

Great stuff!

Huggy

Statistics: Posted by Jon Huggins — May 12th, 2012, 9:12 am

Amos,

I'd like to get a copy of that Excel planning tool- bcox (at) bretcox.com. Appreciate your work.

Recently, have been flying long cross country in my L-39 and observed the same data as Rich and Daryl have offered. Rich's point about a boat on plane seems spot on and was a big ah-hah moment. Small reductions in power at this point can result in the aircraft coming 'off plane' and disproportionate reductions in TAS. Let the aircraft accelerate when leveling off then reduce power to the point on the airplane where it gets the most TAS for the buck, in my airplane it is 98.5%.

Daryl's advice about staying high in close is also spot on, in my experience, it might be better to stay VFR if it will allow you to plan the latest possible descent rather then being stepped down from the flight levels farther out.

I'd like to listen to Rich or Daryl's more specific advice regarding power settings and best practices for each phase of flight.

Also, does anyone have experience with changes in CG or other to improve performance? There is an old Reno racers trick whereby they operate with the CG near the aft limit and it does seem to markedly improve the TAS of a stock airplane.

-Bret Cox

Statistics: Posted by Bret Cox — May 12th, 2012, 7:27 am

Hey Jon,

The L-39 has a TAS indication as the small needle on the same airspeed gauge.
Performance calculation is usually based on TAS so it is worth referring to this needle.
IAS for pressure altitude should be 195IAS at 16,500 and 185IAS at 23,000

Descent - The book does call for a descent at idle. I personally don’t like to do so as I don’t want to cool shock the engine. Not based on anything that I found in the documentation and the L-39 experienced pilots might say it is not an issue but I prefer to take it out of idle every 3-4 minutes. The descent profile I use addresses this issue:
– in a perfect world, it is best to stay high for as long as you can and descent clean, at idle close to VNE. This provides you with max time in high altitude and min fuel burn as you descent.
However, with max speed of 250 below 10,000’ we can’t do that. I did some testing and got to a descent rate of 2,200 at idle in order to keep below 250Kts. This means about 4 minutes\~20Miles for the last 10,000’.
I do the initial descent to 10,000’ at Idle at a distance of 2xAlt (start my descent at 32 miles if I am at 16,500, start at 46 miles if I am cruising at 23,000’). This gives a descent rate of appx 3,200-3,400FPM. Level at 10,000 for one minute, engine to appx 80% and then continue the descent at 250kts from 10,000 to the airfield (I use 70% as minimum RPM below 2,500’ AGL).

Obviously, ATC will have significant effect on this. On a clear day I cancel my IFR below 18,000’ .

From what I have seen so far, Idle descent gives about 65 to 75 GPH at all altitudes. Never saw it below 65GPH on my Shadin.
If you like Excels, I can send you an Excel I prepared that details all the calculations from the book. I am trying to simplify it so all that will be needed is to enter a range and it will give you recommended Alt, TAS and expected fuel along the route.

Statistics: Posted by Amos Vizer — May 12th, 2012, 5:15 am

Will you get a TAS indication in the L-39? Or only IAS?
If I'm doing my math right, am I correct in figuring that max range is about 205 KIAS at 16500,... dropping to about 190 KIAS at FL230?

Also, for descent purposes, to minimize your fuel burn (no wind), wouldn't you use idle/clean, and and airspeed of something near L/Dmax?
What is the fuel flow at idle at FL200, 10,000' and sea level?

Sorry for all the perf questions! I figure I'll be flying the L-39 more at sometime in the near future, so I better learn about it when I can.

Statistics: Posted by Jon Huggins — May 11th, 2012, 8:41 pm

Thanks Rich,
Will be going for apps 440 mile legs, each with 2 alternates.
Are you planning to attend the Chicago Jet Blast?

Statistics: Posted by Amos Vizer — May 11th, 2012, 6:45 pm

Ami,
You are thinking correctly. When you level off let it accelerate to about 220 KIAS and then set about 98% N1. I have experimented a lot. I've seen as low as 96.5% N1 but 98% is a good starting point. It's a lot like a boat coming up on plane. A 3 gph reduction in fuel flow can cause an 8-10 Knots decrease in ground speed. Each aircraft is slightly different. The book answer is 100% and 320 KTAS. My technique gives you about a 300 KTAS average over 60-75 minutes at cruise. The fuel flow drops a greater percentage than KTAS.

Plan your descents for 1500-2000 fpm. You will have to be below 80% nearing 10,000 ft to keep a clean aircraft below 250 KIAS. Just remember to give yourself options. Go to long runways, preferably airports with multiple runways or with usable alternates close by. "Stuff" does happen as you know from your air force days.

Safe trip...

Rich Hess

Statistics: Posted by Richard Hess — May 11th, 2012, 9:16 am

1. Based on the POH, at
16,500ft: 122GPH @262Kts TAS = 2.15MPG
23,000ft: 114GPH @273Kts TAS = 2.4MPG
26,000ft: 108GPH @281Kts TAS = 2.6MPG

Startup, Taxi, Takeoff, Landing = 35 Gal
Climb and Descent = ~50 Gal (100 Miles)
50 Gal = Spare

200 Gal available for Cruise
16,500ft: 2.15MPG = 430 + 100 = 530 Miles
23,000ft: 2.4MPG = 480 +100 = 580 Miles
26,000ft: 2.6MPG = 520 + 100 = 620 Miles

Statistics: Posted by Amos Vizer — May 10th, 2012, 7:54 pm

Two questions:
1. What speed at FL230 will give you max range in the L-39?
2. What kind of pitch angle will you be at with the L-39 in idle and max range speed? How about idle and max endurance speed (or L/D max)?

Statistics: Posted by Jon Huggins — May 10th, 2012, 7:06 pm

Good question. I personally am more conservative than your flight planning, as I normally plan fuel stops at 400-450 miles, and I usually have the oxygen ready at the flight levels in case anything happens or I start feeling funny. Rich Hess at IJ has done some very long legs and monitored his fuel very closely, but always tested the aircraft at altitude prior to the overseas flights to be certain that it met the proper calculations. If possible, have Center keep you high in close, as they will try to step you down early and this greatly increases your fuel burn. Hope to see you at Dekalb.

Statistics: Posted by Darryl Christen — May 10th, 2012, 2:35 pm

During a seat belt change out, the mechanic needed "better access" to the rear cockpit right lap belt attach point. Despite being informed that the canopy was "hot", seeing the right armrest warning placard, the safety pin in the armrest handle and the red warning flag on the pin, he was persistent and successfully raised the armrest. Regardless of any concern about the dating on the charges and their "age", we can attest to their absolute effectiveness! Thankfully, the canopy was full OPEN (jettison can only occur from full CLOSE). The canopy fired upward, opening an estimated further 10 inches at the front while rotating about its rear attachments and causing minor sheet metal damage to the turtleback. The catapult tube/remover sections, having reached full travel, then separated and the canopy slammed 'closed" without restraint, striking the mechanic on the head (luckily he was kneeling on the aft seat facing aft and no arms or hands were outside the cockpit). Damage was inflicted upon the windshield rim, the normal motor/chain system (including motor/actuator and sprockets/gears) and the mounting rails for the normal operation mechanisms. Additionally, the reactionary downward force drove the mounting assembly on the floor to crush the center channel/tunnel and damage the flight control connection links/tubes which connect the front and back control sticks to each other and to the flight control systems. With these connector tubes depressed 20 degrees at the approximate midway point (fore and aft), a shear failure of the rivets connecting the tubes to the stick base fittings occurred. Upon reviewing the manuals in preparation for undertaking repairs, it has been determined that it is possible that the safety pins in each initiator may not be the correct type, thus permitting the initiator(s) to not be fully safetied. (see T.O. 1T-33A-1, figure 1-37, pg 1-63). With all safety pins "installed", raising the armrest alone should not have fired a properly safetied initiator. While this is a "contributing factor", the prime cause was human error-failure to observe warnings and briefing.

Statistics: Posted by Douglas Matthews — May 9th, 2012, 6:54 pm

Hi there,

I am getting ready for the flight to the Jet blast in Chicago.
Calculating range and fuel burn and wanted to get feedback from those of you that have more experience on the L-39.

I am planning to fly at 23,000' which gives max range with no need to fly with the oxygen mask on my face (I have a mask).
My calculation shows that i should expect a range of 500 miles and land with about 75 gallons.

Does this make sense?

Statistics: Posted by Amos Vizer — May 4th, 2012, 3:43 pm

Gentlemen,
I've been contacted by someone who is interested in either buying or renting some Hunters. Must be two seaters, flyable, good condition and records, and decent spares if possible. Please feel free to contact me off-line at 404-964-4885 or hess737@aol.com. Thanks in advance. Rich Hess

Statistics: Posted by Richard Hess — April 29th, 2012, 7:30 am

She looks gorgeous Phil. Good luck with the sale... Now where's my lotto tickets?

Statistics: Posted by Baz Ford — April 23rd, 2012, 4:16 pm

As did I as soon as heard about this.

In thinking a bit about this I have to wonder if they are trying to stop the Collings Foundation and anyone else who has similar ideas? But this could further put a halt on trying to get parts for their aircraft that were U.S. made or designed by the U.S. and those parts are outside of the U.S.

It's bad enough we have to deal with U.S. Customs, the FAA, insurance companies, fuel prices, and now some of us have the military to deal with.

After round one of the government wanting to destroy my aircraft because it is on the strategic arms list (and they may have wanted me to spend the cost and have me destroy it), I have dropped my membership with the National Museum of the Air Force.

Statistics: Posted by Scott Vetter — April 23rd, 2012, 9:28 am