Yak-7b engine dies during takeoff run??

[ChivasRx]

New to this version of IL-2, but played the original in 2001 and 1946 a few years after. Just started BoK on Thursday with the P-39 just getting a feel for the plane, tried a few landings which were pretty good and a few small dogfights. So far,VERY impressed. So I want to check out one of the tailgraggers, Yak 7b, and see if I can land it successfully. I can, but the issue is takeoff. Using "normal" flight, not expert, on the runway, throttle up, get the plane moving straight with some left rudder, slowly throttle her up, tail wheel comes off the ground, gaining speed and getting a little excited to rotate, then the engine just totally dies. Happens at about 75 mph and it seems to be caused by an automatic change (normal mode) to the mixture. The second it changes the mixture, to 75% I believe, the engine just stops. This mostly happens on dirt runways. I tried a bunch of times with the exact same result. Tried to search for some info online, and not much came up. I did read about overheating issues with both oil and water, and then tried expert mode, trying to warm the engine before take off then opening the radiators with several different mixture levels because the engine was dying every single time, and nothing, engine dies mid takeoff run. Btw, these are during single flight scenarios, airfield is mid map on the west coast. Great area! Anyway, I was getting a little ticked and decided to do a few dogfights, thinking I'd start in the air and not deal with taking off. Tried a different area and I must have erred as I was on a concrete runway with two other planes in my flight. So, throttle up, etc etc...., and lo and behold the plane accelerates passed 80 and it's looking good, keeps going and boom, I'm off the ground! Had a great battle too. Did another one, no problem. This morning I'm thinking all is good on the concrete runway, trying a flight, mid takeoff roll, the engine dies. I'm beyond puzzled, and beyond ticked. Tried it again, maybe slightly slower advancing the throttle, maybe, and no issue with the engine.  Like I just said, I am totally puzzled. Anyone familiar with this? Frustration is an understatement, especially because I think I really like this plane! Seems to have a great gun and flies very stable. I would really appreciate any help with this issue. 

 

Thanks!

Edited August 12, 2018 by ChivasRx

[OrLoK]

radiators opened? no overheating?

[WheelwrightPL]

1) Check if the engine governor is set to too low rpms

2) Check if propeller pitch is too high (ie. coarse)

[ChivasRx]

When I went to expert mode, I definitely had both radiators, oil and water, wide open. In looking at the gauges, nothing was ever overheating from the eight seconds or so takeoff run before the engine shut down. Really strange. Most times, including when I had success taking off from the concrete runways, I was in normal mode where the radiators should be controlled automatically. 

[-SF-Disarray]

The prop is striking the ground. I don't know exactly why it is doing this, though. I had the same issue as you, just random engine death on the takeoff run. I had a buddy watch a takeoff run for me and he confirmed what I suspected. For some reason the nose will dip and the prop will catch the ground, killing the engine. Apply a little back pressure on the stick, or trim nose up a little and the problem should correct itself. Don't over do it though, you only want enough to keep the nose up and the prop clear of the ground. Too much and the plane will try to lift early and you run the risk of a stall.

[busdriver]

1 hour ago, WheelwrightPL said:

1) Check if the engine governor is set to too low rpms

2) Check if propeller pitch is too high (ie. coarse)

 

You can not set the governor, it works automatically. Borrowing heavily from a post I made last December.

 

Let's stop you for a moment to clarify terminology. It's Fine and COARSE, not Course. Think sandpaper, fine grit and coarse grit. Think the of the propeller blade taking a small bite of air (Fine) at a high RPM or an increasingly bigger (coarse) bite of air at lower RPM. Feathered is a special case of the coarsest setting of blade pitch. 

 

While you see variation in RPM while manipulating both throttle and prop control, you really need to embrace the fundamental concept that the throttle controls manifold pressure (or in the case of the Spitfire the Boost gauge) and the prop control controls RPM. It's the unseen propeller governor that is slightly varying the RPM as you move the throttle or accelerate in a descent or decelerate in a climb.

 

So set your desired RPM with the prop control...set your desired MP/Boost with the throttle. Repeat that until you internalize this concept. 

 

10 minutes ago, Disarray said:

The prop is striking the ground. I don't know exactly why it is doing this, though. I had the same issue as you, just random engine death on the takeoff run. I had a buddy watch a takeoff run for me and he confirmed what I suspected. 

 

This is a good idea, worth investigating. ChivasRx perhaps you should record your takeoffs and review the tracks. 

[ChivasRx]

Disarray, you sir are the winner! I did a bunch more takeoff runs, maybe 10 and the first five or so ended with the engine out. Even started parked the first time to see if that made any difference. The last two unsuccessful tries happened exactly when the tail wheel came off the ground, so on the next try, I did exactly as you said, kept a little back pressure on the stick to keep the tail down. No problem. Just did a circuit and landed. Awesome. Tried again, took off fine, did a another circuit and floated a bit on landing. When all wheels were down, I got on the brakes a little early and the tail lifted and bang, engine was out. I was coming back to report it had to do with the tail off the ground! Lol which is true, but the actual cause was the prop. WEIRD! I was thinking fuel flow maybe. Hahaha I did notice the propeller was dinged up once or twice, but never made the connection during my moments of disbelief. 

 

Thank you very much guys! 

Edited August 12, 2018 by ChivasRx

[-SF-Disarray]

Glad I could help.

[69th_Panp]

Trim is your friend %^)

 

[Freycinet]

If this is Chivas from the old Ubiforums then greets to you from Freycinet and welcome to this new generation sim!

Edited August 13, 2018 by Freycinet

[Tony_Kito]

I had the same issue transitioning from the Yak-1 to the 7B, but then I realized the reason I kept prop striking is because the Yak-7B has a distinctly smaller landing gear than the Yak-1, which means you have less room to nose down for your takeoff run.

[-TBC-AeroAce]

Sounds like mixture to me.

[novicebutdeadly]

On 8/13/2018 at 7:01 AM, busdriver said:

 

You can not set the governor, it works automatically. Borrowing heavily from a post I made last December.

 

Let's stop you for a moment to clarify terminology. It's Fine and COARSE, not Course. Think sandpaper, fine grit and coarse grit. Think the of the propeller blade taking a small bite of air (Fine) at a high RPM or an increasingly bigger (coarse) bite of air at lower RPM. Feathered is a special case of the coarsest setting of blade pitch. 

 

While you see variation in RPM while manipulating both throttle and prop control, you really need to embrace the fundamental concept that the throttle controls manifold pressure (or in the case of the Spitfire the Boost gauge) and the prop control controls RPM. It's the unseen propeller governor that is slightly varying the RPM as you move the throttle or accelerate in a descent or decelerate in a climb.

 

So set your desired RPM with the prop control...set your desired MP/Boost with the throttle. Repeat that until you internalize this concept. 

 

 

This is a good idea, worth investigating. ChivasRx perhaps you should record your takeoffs and review the tracks. 

Or just fly a Bf 109 or Fw 190 :-) :-) :-)

Edited August 14, 2018 by novicebutdeadly

[Ribbon]

On 8/12/2018 at 10:48 PM, Disarray said:

The prop is striking the ground. I don't know exactly why it is doing this, though. I had the same issue as you, just random engine death on the takeoff run. I had a buddy watch a takeoff run for me and he confirmed what I suspected. For some reason the nose will dip and the prop will catch the ground, killing the engine. Apply a little back pressure on the stick, or trim nose up a little and the problem should correct itself. Don't over do it though, you only want enough to keep the nose up and the prop clear of the ground. Too much and the plane will try to lift early and you run the risk of a stall.

Happened to me once, waited to long without pitching up, prop kiss the ground but didn't look bent or damaged.

Maybe DM is so good, prop won't get to much damage slightly touching the ground but torque shaft get broken.

[kestrel79]

Welcome. Totally remember your name from early 2000s IL-2

[Finkeren]

The Yak-7b is indeed far more prone to prop strikes during take off on account of it being closer to the ground. Once you correct for it, it is no issue.

 

 

[ChivasRx]

Thanks for the warm welcome guys! I do remember both of you, Freycinet and Kestrel...always amazes me how small these communities are, and what a joy it is to be a part of it. Happy to report zero issues with the Yak now. ?

[BlitzPig_EL]

I do remember your name as well.   Welcome to the new place.