Cylinder Head Temp and Carb Air Temp

[fuelpumps 3]

I have been experiencing spark plug fouling in almost all of my T-28 flights at cruise alt. I learned that I have to keep the CHT at an acceptable temp, which is not too hot and too cold, also. That includes managing MAP and cowl flaps like every time at almost all phases of flights, even on the ground. I have to make periodic change in mixture every hour. I am having a lot of fun, but confused at the same time, especially the concept behind MAP. I might set the MAP too low in high RPM, but how? What did I do? Did I decrease the prop when the throttle is in high RPM? What should I do to make a proper adjustment to the MAP since in my understanding, MAP and RPM are in conjunction with Throttle and Prop. I nearly see no difference in both parameter when I apply various power in both knobs. I am not even sure what I am asking now since it is too overwhelming  :fool: but your enlightening about MAP and RPM would be just great

 

thanks

 

[bob44 1]

Hello.

I do not have the T28 at the moment, but can help with general MP and RPM settings.

To increase power, increase RPMs first then MP. To decrease power, lower MP first then RPMs.

I do not have the exact specs for the T28. Should be in the aircraft's docs? Take off, climb, cruise power settings.

 

As an example, for the A2A B17, with a similar engine. Take off at 46MP and full RPMs. For 5 minutes. Reduce the MP, throttle, to 38MP and 2300RPM, prop lever, for climb. At altitude, set for cruise power, which can vary from a faster 34MP and 2200RPM to a slower 29MP and 2000RPMs. Descend at 29MP and 2000RPM to help keep carb temps warm enough. Once in the pattern, set 20 to 25MP and 2200 or 2300RPM. Here is where MS has things very wrong. Increasing the RPM should increase drag in RL. But it is backwards in the flightsim. Some developers have this modeled right, latter A2A aircraft for example, but many do not.

 

Fouling during cruise might be too rich a mixture. do not know if this aircraft models auto rich, auto lean? Use a leaner mixture setting, see if this helps.

[fuelpumps 3]

Hello.

I do not have the T28 at the moment, but can help with general MP and RPM settings.

To increase power, increase RPMs first then MP. To decrease power, lower MP first then RPMs.

I do not have the exact specs for the T28. Should be in the aircraft's docs? Take off, climb, cruise power settings.

 

As an example, for the A2A B17, with a similar engine. Take off at 46MP and full RPMs. For 5 minutes. Reduce the MP, throttle, to 38MP and 2300RPM, prop lever, for climb. At altitude, set for cruise power, which can vary from a faster 34MP and 2200RPM to a slower 29MP and 2000RPMs. Descend at 29MP and 2000RPM to help keep carb temps warm enough. Once in the pattern, set 20 to 25MP and 2200 or 2300RPM. Here is where MS has things very wrong. Increasing the RPM should increase drag in RL. But it is backwards in the flightsim. Some developers have this modeled right, latter A2A aircraft for example, but many do not.

 

Fouling during cruise might be too rich a mixture. do not know if this aircraft models auto rich, auto lean? Use a leaner mixture setting, see if this helps.

 

Thanks for your time answering the questions. It gives me a big picture of engine management. I am not a real pilot so this is pretty overwhelming at first. However, at cruise, the Cylinder head's temperature is relatively low even with supercharger and high rpm (mil speed). Descending makes the temp even lower even with cowl flaps closed. Normally, one tends to decrease throttle when descent, but then it will make the cylinder head temp even lower. Sometimes before I was on final approach, the plug had been in poor condition. 

 

It does help after I read your reply several times, there are somerelevant ideas of what you are explaining. Although I dont own the B-17, T28 was built in almost the same era.

 

The spark plug fouling is the most common failure in T28 Trojan, that's the manual says and that's what happened to most all of my first flights. Thanks Bob.

[bob44 1]

Hello.

When cruising, you want to keep the RPMs low for efficiency. Both fuel and faster speeds. A low MP and high RPM should give cooler head temps. Reads like this T28 models this accurately.

On descending you do not want to pull the MP back too far. 20 to 25MP at the lowest. RPMs in the 2000 to 2200 range.

In RL, you prop up (not too much) to increase drag some when descending. And on final go to full RPMs in case of a go around. Full thrust is available if needed. Do not know if prop drag is modeled here or not.

Too low a MP and the outside air can push the prop, fouling plugs. Again, reads like this T28 models fouling plugs well.

I used the B17 example because it uses the same Wright 1820 engine as do many T28s, though set up differently.

Iam going to have to get this T28. Sound like my kind of plane.

[fuelpumps 3]

Hello.

When cruising, you want to keep the RPMs low for efficiency. Both fuel and faster speeds. A low MP and high RPM should give cooler head temps. Reads like this T28 models this accurately.

On descending you do not want to pull the MP back too far. 20 to 25MP at the lowest. RPMs in the 2000 to 2200 range.

In RL, you prop up (not too much) to increase drag some when descending. And on final go to full RPMs in case of a go around. Full thrust is available if needed. Do not know if prop drag is modeled here or not.

Too low a MP and the outside air can push the prop, fouling plugs. Again, reads like this T28 models fouling plugs well.

I used the B17 example because it uses the same Wright 1820 engine as do many T28s, though set up differently.

Iam going to have to get this T28. Sound like my kind of plane.

 

Thanks Bob. Excatly, just did a crosscheck of what you said about MAP and RPM and the parameter mentioned is not poles apart. It is preferable to apply 2000 RPM and 20 MAP when doing rapid descent. I wonder, how did they manage to keep the spark plug in a good condition during dogfights and aerobatics? I didn't knew that plug could give so many troubles. 

 

If you re not in hurry, there is a freeware (donationware) version of AntsAirplanes T28A. The A model has the same wear and tear engine feature although a slightly different cockpit config. However, it is much slower (T28 800hp. T28 B/C/D 1425hp). I really want to get into the B-17, but I am waiting for their Piper Cherokee. Seems they might release it before this month ends.

[bob44 1]

Spark plug fouling is common on piston aircraft engines. With too low a power setting. Even on todays GA aircraft.

Managing the engine right is the key. 

I will be definitely checking out that T28.