All I have to say is that I’m jealous that you know how to format posts on our site better than I do. 
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Same here. I’m using the information in this series to make an informed decision on which to purchase during the Summer sale. Visually, I like the L-29 a bit more than the C-101 but so far it seems like the latter might turn out to be the better trainer (at least for me).
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If you can swing it with the sale why not get both? Each gives you a particular feel and experience in terms of East and West way of doing things, from ergonomics in the cockpit design to the avionics itself. I fly both regularly and enjoy them immensely.
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Setting up the gunnery range
Well, here we are in Nevada - the kind folks at the US Air Force welcomed the trainer test crews from both teams to use their gunnery range, provided they get their hands on all the performance data of the Warsaw Pact weaponry. How nice of them.
The hard part for me about actually comparing guns effectiveness / range / accurancy is that I’m hardly a strafing expert - but then again, this is a good opportunity to learn, so I’ll give it a go - but I absolutely welcome any technique advise you may have.
I figured I’d try to minimise variation by setting up a simple gunnery range scenario to try and minimise the PIFU factor (pilot-induced-fudge-ups).
Sunny morning, 20 degrees Celcius, 5-knot southerly wind. Some old M113 APC’s on the salt flats. I’ve also put a big nice oil fire next to the targets to make it easy to see the targets and the wind direction.
The valley floor is 5300 ft from MSL so there’s a little bit of altitude to deal with - but you can’t choose what elevation your real targets are either, so we may just as well test the performance up here.
My initial plan for the testing (this may change in due course) is to set up on a 10,000 ft barometric altitude rectangular (i.e. about 5,000 ft AGL) pattern with the attack runs from North to South. I’ll do a hard wings-level pull-up after firing, followed by a 90 degree climbing turn to the East, then around and back.
I don’t have any official data regarding speeds, configuration, sight settings, slant range etc. for a gun run for either aircraft, so I just have to start somewhere I guess.
I’ve only just started, but at the moment I’m trying out clean configuration, full throttle, 5-10 degree nose down runs with the C-101.
Starting at 10k at 200ish knots ends up with a pull-up at 6000 ft (700ft AGL) at about 360kts, which doesn’t exceed airspeed limitations and is fairly controllable, although you do want to have a bit of nose down trim to start with or you end up spending too much time retrimming to have time for a stable shot.
In terms of lethality, it seems to take about 4 hits of the DEFA 30mm to kill an M113. The 5th round set them ablaze every time but some absorbed 4 without a fire.
I need to start setting up very clear parameters for the dive to start extending the firing distance out and actually try to form an opinion on accuracy - I haven’t figured out the drop yet so I’ve been going in close. TacView should come in handy.
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Gunnery range - initial impressions
So firstly I have to say, this is a really interesting exercise. My ‘data’ so far is far from conclusive and definitely more anecdotal than hard fact - so take it with a grain of salt…but the process is fun.
Here’s the pattern I’ve been flying. The attack turn and run starts at 10,300 ft MSL / 5,000 ft AGL at circa 200kts and around 10-15 degrees nose down attitude.
The first difference when diving in is the visibility out of the cockpit. The C-101 has a less cluttered cockpit, however the wide dashboard doesn’t allow the pilot to peek down and ahead as much: in the L-39 you can tilt your head to the side and see down and ahead past the HUD assembly:
That’s what it feels like, anyway - it seems easier in the L-39 to offset from the target just by a bit, keep the target on sight and remain in level flight.
Once you’re accelerating down the slope and trying to do gunnery ‘by the numbers’ (i.e. fire at a decided altitude / attitude rather than at point blank range), the layout of the C-101 cockpit is more use friendly. You can look through the HUD and keep an eye on the altitude, the artificial horizon and the airspeed quite easily - a lot more so than in the L-39, where the digital altimeter scale is smaller and lower down in the cockpit:
When it comes to weapons effectiveness, there’s definitely a difference too. The rate of fire does make a difference, in both good and bad. I had instances with the DEFA where a short 0.5 second burst with a few direct hits wasn’t enough to take out an M113, whereas the GS-23L seems to send enough lead downrange that if your aim is true, a very short press of the trigger is enough to take APC’s out reliably. The DEFA potentially feels more accurate at distance at the 10-15 degrees diving angle - but I need to test more to be sure.
The more modern C-101 HUD has a nice digital depression status display (which matters little) - the smaller pipper is arguably better than the L-39’s.
The L-39 HUD assembly is obviously bulky but ultimately there’s little functionality difference.
The C-101 has a noticable nose-down moment from the recoil. The L-39 shakes a bit but the nose remains put.
It sort of feels like this: with the DEFA you can do multiple relatively accurate passes from potentially a bit further away (as I said, unsure at this point) but you may need to come back to finish the job, whereas the GS definitely delivers in one go if you dare get close enough. In saying that, the GS really only gives you a couple of passes, as the rounds run out a lot quicker.
Up close, the GS is a deadly weapon.
Neither gun let’s you ‘snipe’ from altitude / distance like the A-10’s monster gun does, of course - you either try your luck from a distance and may achieve nothing but you’re more likely to survive…or you wait until throwing distance and risk your hide but will likely get results. No free lunches.
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Superbly done. I’m actually working on missions for both these aircraft and have been starting to relearn flying them as well. Curious, how did you determine the angle of your dive in both aircraft? Also, how did you determine the angle setting of your gun-sights on both aircraft?
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Mostly just guesswork and trial and error, to be honest. I tried to find some stuff online about strafing - didn’t come up with much.
One article written by a real air force general made a reference to 5-15 degree dives. Another sim forum discussion talked about ‘steep’ dive angles resulting in less ricochet danger for blue troops in the vicinity but didn’t specify degrees. Someone had done an A-10C video of steep dive gun runs at 30-45 degrees but I don’t know if that was based on any real life data.
I just figured I’ll tackle the variables one-by-one: a set 15-degree dive from a set 5000 AGL altitude with a set 200 kt starting speed. Fire at a set altitude. See how short the rounds land. Add more depression. Go around and do it again, see if the rounds land on target or whether the distance is too great and there’s too much dispersion.
I’ve only just started this exercise but I thought I’d try to figure out the depressions for a ‘shallow’ (15-degree) and a ‘steep’ (30-degree) dive to come up with a couple of profiles that I know should work. The steep dive should require less depression, as there’s less horizontal distance…but I’m not that far yet.
Part of the issue is that with these aircraft, you don’t really have the ammunition to ‘walk your shots’ - you need a pre-set template (dive angle, speed, AGL altitude and sight depression) so that when you pull the trigger, you can be relatively sure you’re close to the mark already.
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Challenges
I have to say…increasing that guns firing distance is…hard.
I definitely think that having those preset profiles helps, and maybe one out of 5 runs I get a beautiful long-range shot where I got the depression right and the rounds arc through the air forever and smash straight into the target.
But the other 4 runs I’m just not quite there and miss…and you don’t have ammo for many runs like with the A-10.
And then frustration kicks in and together with target fixation the results can be detrimental. I ended up scratching my belly on the desert floor…which did make me wonder about whether the damage model is quite there yet, as I’m pretty sure most of the modules would have just blown up, whereas I kept flying. The engine did quit and I had to flounder down to the salt flats within the next couple of minutes:
Pretty keen ground crew we’ve got - they had the ladder ready in the middle of nowhere, which was nice.
I think this comparison work will take a little while, as I’ll be doing this when time / enthusiasm allows and this gunnery practice has actually been pretty hard. Hence I thought I’d do a little ‘summary so far’, in case anyone wants to take advantage of the current sale.
Summary so far
Both modules are great (yeah, not helping with your decision-making, am I). Both the planes require the pilot to fly well, as you don’t have the available power to be sloppy. At the same time, they are both predictable and benign (to a point) so they are great to learn in.
The airspeed range is such that while things happen plenty fast, you at least have some hope to stay ahead of the plane and get your checks done before you overfly the target/waypoint or get lost - something that’s easy to do in the faster jets, for me anyway.
In short, you can’t go wrong with either - and chances are you’ll be pleasantly surprised how fun it can be to fly an underpowered jet with limited systems: there’s also the upside that when you do hop into a full-fledged warplane after flying the trainers for a while, you feel like you’re in a super-futuristic rocketship - so you get a secondary kick out of it. 
Anyway, to give some comparisons - quick bullet point notes:
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The C-101 has a Western cockpit and hence transitions well into learning Western planes. The L-39 is the opposite and has the option of showing speeds in kmh and meters, which helps you in learning the Eastern Bloc aircraft. You can switch the gauges to knots/feet in the L-39 though - which I’ve done for this comparison, as constantly switching my brain between the two units hurts too much.
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The C-101 cockpit provides more nice-to-know information to the pilot - the L-39 cockpit layout is quite quirky and bare in comparison but it does the job.
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Overall, the C-101 can carry more punch for ground pounding. The L-39’s gun firing rate gives it more punch per gun run at close range, but it runs out quicker.
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The L-39 can do night attack better because of the illumination bombs.
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C-101 has more range, but I don’t think I’ve ever ran out of fuel while playing around with the L-39 either, so this isn’t a big advantage.
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I can’t help still feeling that the L-39 is slightly more fun to fly. It might be just a bit more nimble or light on the controls, although I haven’t done a comparison of the roll rates.
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The L-39 is an older and potentially more polished module.
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The C-101 still had things to iron out that were impacting the experience just a few months ago. I still think there are things going wrong (buggy) - for example the AoA meter is giving way too big readings. It only matters if you’re trying to learn flying at a specific AoA…but if you do, it does matter.
So there you are. I’m going to keep plugging away at this over time, but that paints a bit of a picture in the interim, I hope.
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Crewchiefs.
Because pilots need heroes too…
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Fantastic stuff…! I have to admit, you’ve spent way more time in the L-39 than I have, so I don’t have a lot of basis for comparison. I’ll bet I’ve only flown the L-39 for three or four hours total. Whereas I’ve spent a lot of time in the C-101CC. So my love of the CC is unfair. 
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You have hit a subject near and dear to my heart, autocannons! If anyone is of a similar interest, if you didn’t already know, Anthony “Tony” Williams has some excellent books that are the current gold standard.
One point I’d like to bring up on you technical breakdown, the DEFA 553 for the C101 is a twin pack, so it’s actually putting down about 43.33 rounds per second as a gun pack. The firing time is still the same 6 seconds, as each gun has 130 rounds. So the number of shells going down range is a lot closer to the GS-23L. @Bearhedge you were right. I thought the 553 referred to the entire dual pack setup, sort of like how the GAU-12 refers to the entire Harrier cannon assembly. I was wrong, you had it right from the get go. Carry on!
DCS has basically zero frag/splash damage modeling, and the “hitpoint” type damage model for ground units is also a problem. Autocannons and rockets both suffer from this implementation, leading to lesser lethality against soft targets. Here’s a real world example of what a 25mm cannon can do:
Real world, the slightly larger 30mm shell has about 2 grams more explosive in the HE shell. The HEDP and AP version of the 30mm is going to have better armor penetration due to the extra weight, and muzzle velocity. Lastly the faster shell, all other things being equal, will be less affected by wind and have a longer range.
Also don’t beat your head against the wall on extended range gunnery. Effective range on the DEFA is about 1500-2000m. Max range is 4000, which would be on an area target anyway. I can’t find solid technical data for the GS-23L effective and max range, but it will be probably a bit shorter.
Great experiment though, and I love what you’ve done so far!
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One Year Later: the C-101 Aviojet has had a plethora of updates since June 2019.
How does it stack up now with what looks like over 100 updates?
I really enjoy the Free MB-339 but am impressed with all the AvioDev updates over the last year for their C-101
The good DCS Modules are digital works of art as far as I am concerned.
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Hi and a late welcome to MS, @YSIAD_RIP!
Wow, it has been a year since these tests! I ended up jumping in the Harrier after the interim conclusions and haven’t been back to the trainers lately - I have been pleased to see the steady updating pace of the C101, though: it would definitely warrant another look.
I’ll see if I can get my head around the updates and get some fresh comparisons done. 
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Thanks, Bearhedge - Free-Time is precious and limited.
Do what you think is best. I see another cockpit update is coming to the C-101 in July, so maybe hold your horses until then. Enjoy the summer!
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We build L-39s with TFE731 series motors (mostly -3s but working on a -5BR). I really enjoyed the thread. Thanks!
Bill
A little data-
Most of the planes come in around 7250 lbs empty. They go out between 5900 and 6200 lbs empty depending on how much weight reduction is done. The CoG is moved aft a LOT which livens the plane up a good bit. Our inspection programs allow for as much as 5" aft the stock limit for racing.
The plane tends to drop a wing a little more on stall but is stalling up to 10 kts slower than a stock L-39. Throttle response and spool up times on the TFE are so much better that we fly the pattern up to 25 kts slower.
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Welcome to Mudspike!
Nice info! Always nice to hear from people who know the real planes.
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I started off training in a stock 39 only to stop before my check ride as the plane was a bit of a dog. A friend passed on information about the L-139 which started me on the path to build one myself.
I ended up doing almost all carbon composite components to fit the motor along with pulling 90% of the stock L-39 out of the L-39 and replacing it with a bespoke Tefzel harness and Garmin avionics suite.
The first plane finished 3rd at Reno in Gold Class on debut. It got a motor upgrade from the -3 to a -4 and would have finished second last year had the pilot not cut a pylon.
After two years of trying, I think I have an inlet that will allow the -5 to breath. I’m hopeful that plane will make it to Reno this year.
I did the projects for fun. A long time friend has picked up the molds and all the development work and is building planes for people. You can find more about that at East2WestAero dot com.
I’m just a nerd with too much time on my hands.
So, how do I dip my toe in the water to fly a L-39 sim?
BTW
I’m so new to all of this that I had to google mudspike
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IMO your best options probably are
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Get DCS World (free) and the L-39 module via Steam or directly from Eagle Dynamics
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Get Microsoft Flight Simulator 2020 (Steam or Microsoft store) and a L-39 addon (either through the ingame store or Simmarket).
Edit:
3. There might also be one for X-plane 11 (soon 12)
#1 is most likely the most accurate plane, but DCSW has small theaters and isn’t very beginner-friendly. It is free though, you only pay for the planes/maps.
Edit:
Either way: we are here to help you with any questions you have about hardware, software, or the games/planes.
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welcome @lolachampcar ! interesting info about the modifications.
there is no good Albatros for X-Plane 11 yet. only reasonably good modeled L-jet is L-29 Delfín from MLADG
there is (was) one good model for older Microsoft Flight Simulator X (FSX) from Lotus Sim
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