Some practical questions

[reflected]

It's incredible how every single day I learn something new about the B-17 or aviation in general when I fly the A2a B-17. I have some questions I couldn't figure out the answers to:

1) "Hold PDI" - when I engage the C-1 autopilot I use this to help center the controls and put the tell tale lights out. Now...what is this exactly? What does it simulate? An order to the bombardier to...do what? Who keeps the controls centered and how? The autopilot is on regardless whether I press this button.

2) Time between overhauls - it can be set to 300h or 1000h. What does it do? If I set it to 300h, will wear and tear be accelerated and things go wrong sooner? Or does this mean that after 300h the parts will be automatically overhauled by my chief mechanic?

3) How do you descend from 25,000 feet so that you don't overspeed, foul your spark plugs, or overcool your CAT? What are your throttle/ turbo settings and your speed?

Thanks,
Greg

[Tug002]

It's incredible how every single day I learn something new about the B-17 or aviation in general when I fly the A2a B-17. I have some questions I couldn't figure out the answers to:

1) "Hold PDI" - when I engage the C-1 autopilot I use this to help center the controls and put the tell tale lights out. Now...what is this exactly? What does it simulate? An order to the bombardier to...do what? Who keeps the controls centered and how? The autopilot is on regardless whether I press this button.

2) Time between overhauls - it can be set to 300h or 1000h. What does it do? If I set it to 300h, will wear and tear be accelerated and things go wrong sooner? Or does this mean that after 300h the parts will be automatically overhauled by my chief mechanic?

3) How do you descend from 25,000 feet so that you don't overspeed, foul your spark plugs, or overcool your CAT? What are your throttle/ turbo settings and your speed?

Thanks,
Greg

Hey there Greg, I am not real familiar with the C-1 auto pilot as I have just started using it so I wont go into that. If I am correct the 300 hour and 1000 hour times are as follows, if you use the 300 witch I use you will have accelerated wear on your engines therefore you will have little problems crop up quicker like oil leaks, worn waste gates, turbo's etc. On the 1000 hour setting I presume that this is the normal setting for a regular check of the engine. When I descend I usually figure out my decent so I will only have to descend at about 500 or 1000 fps and by putting the turbo's at 8 and reducing the manifold pressure to 25 or 30 " this keeps the carbs warm as I descend and the engines do not cool off to quickly. Once at 9000 ft I turn back on the air filters which help warm the air to the carbs. At a guess I think that PDI stands for Pilot Direction Indicator which is set for the heading to follow for a bombing run.
Hope this helps you out
Keep smiling
Tug

[reflected]

Hi Tug,
Thanks for your reply!
I guess I'll leave it on 300h to have an accelerated wear. It makes things more interesting. I'll try not to take a broken hydraulic line personally, though

I use the same method when descending, using high turbo and low throttle to keep the carburetors warm. The only problem is that even with 20" throttle I end up going reaaaally fast, too fast for my crew's liking.

[Tug002]

I usually try to descend at around 200 mph which seems to keep everyone happy I have had complaints though, short field landings dropping quickly after clearing the trees will make them say some interesting comments, also barrel rolls will get you some more but if you try that make sure that you are high enough as the B-17 is slow at rolling I have found the run away turbos and engine fires the most interesting As for the descent I usually plan from quite a distance when coming down from 30000 ft and do it slow as no to upset the crew.

Keep smiling
Tug

[robert41]

There is a good thread on the C1 Autopilot. Will take some searching to find it again.
I keep the TBO at 1000hrs. Still plenty of issues at this rate. My most interesting are the runaway turbos. One other interesting one was last summer, right after take off, I noticed my number 4 fuel tank was only half full. Checking the fuel screen, it was draining out at about 1 gal per second. After a quick landing, maintenance showed just a fuel leak. Must have torn open the fuel tank.
Descending I go no lower than 29MP. 500fpm descent. From 25000ft starting at about 150nm out. Speeds keep about 200 to 250IAS. If the carb temps get too cold, up the turbo boost.

[reflected]

Thanks for the replies. I have some other questions that have arisen:

My co-pilot has been handling the cowl flaps correctly when I told him to do so, but yesterday he would keep them where they were, regardless the temperature. On the other hand, he did manage to handle the intercoolers correctly. The only thing I changed was installing a few more repaints.

Then there is the question of fuel consumption. I know accu-sim doesn't like time acceleration, so I flew a Schweinfurt mission on 4x max. Yet there was so much fuel left in my tanks, I couldn't believe. Even 2x or 4x time acceleration affect fuel consumtion?

Does the electric suit heater work? When the cabin is cool despite the full on heating, does it help to turn it high?

Thanks,
Greg

[Jacques]

Are you sure Cody is ignoring the cowl flaps? Are your cylinder head temps unusually high? Adjustments to the cowl flaps are relatively small and quick. You can check to see if there really are no adjustments being made by varying your engine settings (larger changes would be better for testing) while watching the cowl flap adjusters in the cockpit. If they aren't being adjusted and your Engine temps are getting pretty high then you may have a problem. Make sure you load in a default flight before loading the A2A B-17. More detail on what you are seeing is always helpful!

[Tug002]

Thanks for the replies. I have some other questions that have arisen:

My co-pilot has been handling the cowl flaps correctly when I told him to do so, but yesterday he would keep them where they were, regardless the temperature. On the other hand, he did manage to handle the intercoolers correctly. The only thing I changed was installing a few more repaints.

Then there is the question of fuel consumption. I know accu-sim doesn't like time acceleration, so I flew a Schweinfurt mission on 4x max. Yet there was so much fuel left in my tanks, I couldn't believe. Even 2x or 4x time acceleration affect fuel consumtion?

Does the electric suit heater work? When the cabin is cool despite the full on heating, does it help to turn it high?

Thanks,
Greg

Hey there reflected, as stated above the changes are quick and usually small. I always keep an eye on all gauges just to make sure that buddy is doing his job. As for time compression you will find that the fuel is not accelerated to co-inside with the adjustments in time. The fuel burns at regular time. As for the suit heaters they will only work for the pilot and co-pilot and will not reflect cabin temp change as I understand it. At least it hasn't for me.

Keep smiling
Tug

[n421nj]

Once established in a cruise climb I'll take over from the copilot. During take off and landing is the only time I delegate the duties. Same goes for the b377.