New issue after latest update??

[divinglyc]

Hi! I am currently on P3D V4.1. and Comanche 250.
I have installed the latest update of A2A A/C in order to fix the ground steering issue.
However, I don't know it's related, after installing that, I found another "issue"?
That is, after I take off, the Manifold pressure began to fall gradually within one min. It decreased soon from 25 to 10! Then I lost power of course.
It happens in all four stock-painted planes and seems only happens in specific airport, like NZDN.. Weird! It does not happen in other airports(at least among those I tried)
What could be the reason??
Thanks!!

[Nick - A2A]

What could be the reason??

Could be carburettor icing. What was the weather like when you experienced the power loss? Certainly if you were taking off in rain or misty weather, pulling the carb heat lever may have been the solution. It certainly seems to catch out quite a few folk!

Thanks,
Nick

[divinglyc]

What could be the reason??

Could be carburettor icing. What was the weather like when you experienced the power loss? Certainly if you were taking off in rain or misty weather, pulling the carb heat lever may have been the solution. It certainly seems to catch out quite a few folk!

Thanks,
Nick

Thanks for replying. I was taking off in a rainy weather. Temp about 6C.
I didn't use the carb. heat. Could it be the reason? Because it happened soon after I take off, in about 1 min.
I tried tonight again. It was not rainy and the temp was 8C. It was all OK. I activated carb. heat, too.
Well, I will keep trying.
Thanks again!!
ps. BTW, the manifold pressure decreases gradually as my altitude increases. That is normal, isn't it?

[AKar]

I was taking off in a rainy weather. Temp about 6C.
I didn't use the carb. heat. Could it be the reason?

Definitely in A2A Comanche. You can almost say that rain = carburetor icing.

ps. BTW, the manifold pressure decreases gradually as my altitude increases. That is normal, isn't it?

Yes, at full throttle the MP you'll see is roughly the atmospheric pressure at the altitude you are at, as this airplane is not supercharged.

-Esa

[Oracle427]

MP will decrease by about 1" per thousand feet as you climb and increase as you descend. Make sure to adjust power as needed when changing altitude.

Carb great shouldn't be on all the time as it runs the engine of power. It shouldn't be on for takeoff it when going around and avoided when on the ground as it can allow unfiltered air into the engine.

Carb icing can occur at fairly high temps in the 20C range. What is important to consider is the moisture content of the air that you are operating in. On humid days beware!

[divinglyc]

MP will decrease by about 1" per thousand feet as you climb and increase as you descend. Make sure to adjust power as needed when changing altitude.

Carb great shouldn't be on all the time as it runs the engine of power. It shouldn't be on for takeoff it when going around and avoided when on the ground as it can allow unfiltered air into the engine.

Carb icing can occur at fairly high temps in the 20C range. What is important to consider is the moisture content of the air that you are operating in. On humid days beware!

Thanks!! So what could I do in my situation?
Taking off in a rainy and cold weather, with carb heat off, but soon after taking off, the manifold pressure began to drop very soon.
What steps should I follow to avoid loosing my power?
Thanks a lot!!

[Oracle427]

Take off and then apply carb heat. It is up to the pilot's judgement ultimately as the reduced take off performance may be acceptable when considering the length of the runway, altitude, aircraft loading, etc.

The engine won't ice up instantly and you have some time to do something about it before it is too late.

Since we don't live in a world where we can go back in time and try events over and over again. I would likely do what I usually do which is use no carb heat on takeoff. I would run up the engine, verify normal performance figures and then take to the runway. When on the runway, I would gradually apply full power, confirm all engine parameters are in the green and where they should be . Then I would watch for normal acceleration and be ready to abort my takeoff if I don't reach at least 75% of my liftoff airspeed by halfway down the runway. Assuming all is well and I lift off, watch and listen. If I see any hint of the engine losing power, I would double check that all controls are where they should be, check the engine instruments and then apply the carb heat if I see the MP coming down despite the throttle being in. The risk of carb icing should be on one's mind especially in humind conditions (monitor the temp/dewpoint spread).

Likewise when descending or landing when engine power is reduced icing may not be noticed until one attempts to add power, be sure to introduce carb heat before reducing power. Monitor the response of the engine to see if there was any icing and then reduce power for the descent. Carb heat runs off the hot air coming off the exhaust pipes. If the engine shuts down, there is no more carb heat making it critical to use the heat when the engine is developing good power.

[AKar]

This doesn't work that well with the particular engine as simulated in the A2A Comanche, but in reality, you'd certainly opt for a full-throttle climb especially in conditions prone to form carburetor icing. Simply put, this shows a minimum surface area of the throttle assembly to the airflow for the ice to form, and mitigates the issue some.

-Esa

[Oracle427]

Yes, some engines are more prone to carb icing than others, but like I said it is at the pilot's discretion.

I personally would not want to have my engine giving reduced power and sucking up dirt to boot at an airport where there are limited options to land. I'd want to get as much performance out of the engine to accelerate and climb up before introducing the carb heat. The reduction in power is very noticeable on some aircraft and I am not familiar with the Comanche. I haven't seen ice form up so quickly that one doesn't have time to address it without rushing. To put it another way, most of the runways that I am flying out of have obstacles all around and are not much longer than 2000 feet so that is why I don't consider the use of carb heat right from the start to be worthwhile. This of course assumes that one has verified all engine parameters are nominal right from the start of the takeoff!

Are there some aircraft where takeoff with carb heat is generally used or were some taught to use carb heat even during takeoff?

I would also never perform a partial power takeoff on these non-turbocharged aircraft. There is nothing to gain by it that I am aware of unless it were done for training purposes to simulate high altitude takeoffs, fast taxi or rejecting takeoff.

[AKar]

Yes, exactly. At full-open throttle, I'd expect it to take some good time to any significant-enough amount of ice to form, and only when comfortably in climb, I'd carefully check the carb heat for any gain in MP while keeping the throttle full-open.

Technically speaking, I'd be hard-pressed to perform partial power takeoffs in most turbocharged airplanes either, if the engine controls are correctly set.

-Esa

[divinglyc]

Take off and then apply carb heat. It is up to the pilot's judgement ultimately as the reduced take off performance may be acceptable when considering the length of the runway, altitude, aircraft loading, etc.

The engine won't ice up instantly and you have some time to do something about it before it is too late.

Since we don't live in a world where we can go back in time and try events over and over again. I would likely do what I usually do which is use no carb heat on takeoff. I would run up the engine, verify normal performance figures and then take to the runway. When on the runway, I would gradually apply full power, confirm all engine parameters are in the green and where they should be . Then I would watch for normal acceleration and be ready to abort my takeoff if I don't reach at least 75% of my liftoff airspeed by halfway down the runway. Assuming all is well and I lift off, watch and listen. If I see any hint of the engine losing power, I would double check that all controls are where they should be, check the engine instruments and then apply the carb heat if I see the MP coming down despite the throttle being in. The risk of carb icing should be on one's mind especially in humind conditions (monitor the temp/dewpoint spread).

Likewise when descending or landing when engine power is reduced icing may not be noticed until one attempts to add power, be sure to introduce carb heat before reducing power. Monitor the response of the engine to see if there was any icing and then reduce power for the descent. Carb heat runs off the hot air coming off the exhaust pipes. If the engine shuts down, there is no more carb heat making it critical to use the heat when the engine is developing good power.

Thank your so much for your detailed explanation! Are you a real world pilot?
I will try this method next time I fly.

[Oracle427]

Yes, and I primarily fly several different models of C172 and C182.

There are several other pilots here, current and retired and there are many who should be given their knowledge and attention to detail. I've learned a lot from them!

The A2A forum is full of a great group and the A2A simulation has such depth that we are attracted to it like moths to a flame.

[divinglyc]

Yes, and I primarily fly several different models of C172 and C182.

There are several other pilots here, current and retired and there are many who should be given their knowledge and attention to detail. I've learned a lot from them!

The A2A forum is full of a great group and the A2A simulation has such depth that we are attracted to it like moths to a flame.

Thank you so much! May I ask one more question?
It's about the Pitot heat.
Should I turn it on all the time or what is the timing of manipulating it? Thanks a lot!!

[Oracle427]

Pitot heat will melt ice off the pitot tube. It can ice up anytime you are in visible moisture and generally should be turned on if you are within 5C of the freezing point and are flying in visible moisture such as clouds or precipitation.

The sim does not model this correctly and you can get a blockage of the pitot tube even in clear, but cold, weather.

In the sim this always manifests as the airspeed dropping to zero. That is one failure mode, but there are multiple holes in the pitot tube. If both holes freeze up at around the same time, the airspeed indicator will turn into an altimeter and read the airspeed where the tube froze up anytime you are at the same pressure and temperature. If you climb or the temperature increases or the pressure drops, then the airspeed will go up and vice versa. Not modeled in the sim though.

Now these planes aren't certified for flight into known icing, so this is just a tool to help save your skin if you end up in a bad spot.

[divinglyc]

Pitot heat will melt ice off the pitot tube. It can ice up anytime you are in visible moisture and generally should be turned on if you are within 5C of the freezing point and are flying in visible moisture such as clouds or precipitation.

The sim does not model this correctly and you can get a blockage of the pitot tube even in clear, but cold, weather.

In the sim this always manifests as the airspeed dropping to zero. That is one failure mode, but there are multiple holes in the pitot tube. If both holes freeze up at around the same time, the airspeed indicator will turn into an altimeter and read the airspeed where the tube froze up anytime you are at the same pressure and temperature. If you climb or the temperature increases or the pressure drops, then the airspeed will go up and vice versa. Not modeled in the sim though.

Now these planes aren't certified for flight into known icing, so this is just a tool to help save your skin if you end up in a bad spot.

Thank you so much for your explanation....