Altitude sickness

[Iron Horse]

Salutations all!

I have an operations question I wish to pose to everyone. I fly the Douglas dc-3 as my choice aircraft. This aircraft has only one small engine mod, but I don't believe it affects too much my problem. Which is, I have troubles at high altitude airports. It seems that no matter what I do(weather included), I cannot develop full power on takeoff, and I just barely make it off the ground before I run out of runway. The Tach (which is obviously incorrect), reads full power. And even after standing on the brakes, and adjusting the mixture under full throttle until the engines reach their highest pitch, I still have my problem. I have tried changing the prop pitch to no avail, I guess if the tach actually read other than 2700 rpm at full throttle, maybe I might have a better chance? Or are the props constant velocity (I just thought of that)?

[N33029]

Salutations all!

I have an operations question I wish to pose to everyone. I fly the Douglas dc-3 as my choice aircraft. This aircraft has only one small engine mod, but I don't believe it affects too much my problem. Which is, I have troubles at high altitude airports. It seems that no matter what I do(weather included), I cannot develop full power on takeoff, and I just barely make it off the ground before I run out of runway. The Tach (which is obviously incorrect), reads full power. And even after standing on the brakes, and adjusting the mixture under full throttle until the engines reach their highest pitch, I still have my problem. I have tried changing the prop pitch to no avail, I guess if the tach actually read other than 2700 rpm at full throttle, maybe I might have a better chance? Or are the props constant velocity (I just thought of that)?

 

The first time I flew the DC-3 was early in the time that I've used FS 2004. I filed IFR LAX to Phoenix Sky Harbor. I might have been up at 16,000' but it's been a long time since that flight. However, pretty soon I developed trouble flying high with the DC-3. My props are constant speed, meaning the prop pitch is adjusted automatically. By the way the throttle quadrant for USB is on sale again and I'm pretty sure if you just get one both engines 1 and 2 will be controlled by your inputs. It is pretty easy to increase the horsepower in the aircraft.cfg file, but I always make a copy and rename it .bak (backup) just in case.

 

Off-topic, I recently bought a delightful video called "Flying the Lengendary DC-3". The 2-D cockpit in FS 2004 is very realistic and with the skill that comes with practice the plane is a joy to fly. In the video the two are very busy with checklists and while I'd like to print or write them out I never bothered with the kneeboard after I wrote the numbers down on a post-it note.

 

All of that said, I would very much like to hear other's experience with the DC-3 since I've had your problem and pretty much like to zip around the Mojave Desert 1000' AGL now. Oh, the cruise speed given in FS is way too high - it is more like 115 knots.

 

Best,

Sean

[mqytn]

The DC3 is my favorite airplane to fly. Once I takeoff in the bird, I will usually fly in it for days. I do not use any addon panels. Keyboard assignments only will allow me to adjust the autopilot on long flights. I can make the bird follow flightplans using the GPS and I can even do ILS approaches when needed. I fly the DC3 in FS9, FSX, and FSX:SE. I have not had enough flying experience with the DC3 in high altitudes so this week I'll fly into higher altitude airports to test it. After flying FSX for a really long time, I think I will dust off FS9 and fly in that world for a while. I'll report back on my high altitude flying.

[PhantomTweak]

Don't forget, the higher you are, even on the ground, the less air there is for the props to push to give thrust, AND the less air to flow over the wings to provide lift to make the plane fly. That's why you need to calculate density altitude, even someplace like Yuma (Field elev. 213'). As it gets hotter, low pressure moves in, many different factors, the airport field elevation gets "higher".

The higher the altitude, and/or density altitude, the longer run you need to take off, given equivalent weight.. Again, slower acceleration, and less air for lift.

Also, much above 2500-3000' density altitude, you really should, as you did, adjust the mixture to maximize your engine's power. You don't have to do it at max power. That's what "run-up" is for. IIRC, you lean the mixture for max cylinder head temp, but it might be EGT, in the DC-3, but I've been wrong before. Again, density altitude matters. Even if you don't use any weather, it's a good habit to get into, calculating density altitude before you walk. Same with take-off run, weight and balance, fuel usage, and all the other things a pilot should know before strapping a plane on.

Hope that helps...

Pat☺

[ponchovilla]

To put it in primitively simple and and oversimplified terms, density altitude is the altitude the aircraft "thinks" it's flying at, regardless of what the physical altitude might be. The "Red Flags" are the "Three H's"... Hot, High, and Humid. Plan accordingly.

[tgibson_new]

Hi,

 

As stated above, what you are seeing is completely normal. BTW, your tach is correct - the props are reaching their normal 2700 RPM. But that's because it's *easier* to reach that value at high altitude, since the air is thinner up there. But since the density of the air is lower there is less for the props to push against, and they do not provide as much power as they would lower down.

 

Also, the other factor in the power equation is Manifold Pressure, and that can drop as well once you exceed the critical altitude of the engines, even with manual leaning. If your MAP gauge is not going as high as it did at sea level, then you are generating less power that way as well.

 

All this tells you that you better have a much longer runway up there than you do at sea level, for a given weight and temperature.

[mikeandpatty]

The DC-3 is unpressurized - therefore, sustained flight above 10,000 ft requires supplemental oxygen, either liquid or gaseous, via an installed or walk-around bottle system. 30 min at 12500 feet is a standard FAA limit, but in the military, it is ANYTIME above 10,000 ft without pressurization, and ANYTIME, SL and above, from takeoff to landing, in tactical jet aircraft - "TOPGUN" be damned -

 

You do not die at altitude from lack of oxygen; there is plenty of it up there (see your engines turning and burning just fine?) - it is the lack of pressure driving oxygen into your lung membranes to be absorbed by your blood that is the problem.

 

Hypoxia is insidious, deadly, and painless.

[PhantomTweak]

and ANYTIME, SL and above, from takeoff to landing, in tactical jet aircraft - "TOPGUN" be damned -

Generally, from the pilots I talked to in the military, they were required to wear their O2 masks from engine start to shut down. If something went wrong and they had to eject, it would help protect their face from injury. If something went wrong with cockpit pressurization, they would be relatively safe from hypoxia, as well. Although the F-18 OBOGS system had some problems in the C and D models. If they weren't paying attention, they could wind up hypoxic without even being aware of it. The Navy developed a Hypoxia Training device to help, but, as you say, it can be so insidious that even with excellent training they still lost planes and pilots.

Another problem the tactical pilots can encounter, especially at higher altitudes, is, essentially, the Bends, just like a diver can. The cockpit only maintains a specific differential pressure, so too high, and it can go lower than you might think. And of course, much above 10,000', if there is a failure of the cockpit pressurization, a seal fails, a bullet hole (as shown in TopGun!) whatever, even with a functioning Oxygen system, they can get the bends.

Sorry, I ramble...

Pat☺

[Iron Horse]

Thank you to all who responded. I have been doing flyins at Peyson, Arizona, and that is where my problem lies. Warm and high. I simply might not be reading the guages right, as I am no longer endowed with sharp eyesight. I am familiar with density altitude having flown years ago "for real!". Nother bat place, nother bat channel.

 

Anyhoo, my thanks to you all.

Jon

N7231S

[liner simpilot]

Hi Iron Horse, I also live in Payson AZ, I haven't ever tried to take off of PAN before in the DC-3, I might try it out but besides Alt the runway appears to be shorter than the 5000 ft length it seems. With that in mind not enough runway might be part of the issue as well as everyone stated here on the forum.. Even a Cessna 182 default FS9 struggles to get airborne no matter what I do. Yet in real life my friend & I go flying there all the time without any issues in a C-205, C-182, I have seen C-150 old one take off as one is based there. Just my thoughts. Kenny

[ronzie]

https://www.simshack.net/media/files/A2A_C182_Pilot's_Manual.pdf

 

is a full manual for the C182S. You can kook at the performance tables and correct for temperatures to get take-off roll. You can also look at the rate of climb at different pressure altitudes and cruise performance as well.

 

https://www.redskyventures.org/doc/cessna-poh/Cessna_172-C172H-1967-OM-bookmarked.pdf

 

has the tables with corrections for temperature (and surface type) easier to interpret. (Download the pdf so you can rotate the pages.) At 5000 feet at 41oF the rotate run is 1255 feet for 2300 lbs GW and to a 50 foot obstacle is 2480 ft. For each 25oF above the 41o standard at 5000 feet increase distance required by 10%.

 

So for PAN the 5200 foot runway should be OK even for 90oF at 5,000 feet surface elevation.

 

Note these manuals are used with the sim models in the case of the C172 it is the A2A version.