Head-2-Head Feature II: DC-10 Versus L-1011

By Ron Blehm (August 2, 2011)

Notice and Disclaimer: Just a few days ago I published a feature called, "The Turboprop Commuter Challenge". Unwittingly, what I had done was to start this brand new feature for FlightSim.Com called "Head-2-Head" where I will present comparisons of various aircraft. These are not meant to be reviews of specific aircraft as it is not my point to bash any certain designers or teams. With a little sleuthing around, I'm sure you can figure out that I used Erick Cantu's EMB-120 or the Dreamwings Q200 in that feature. It was not my point to have you walk away from that article thinking, "Geez, that Antonov really sucked." In fact, considering the power and range and lifting ability of the real-world model, it has sold far more than the EMB or Dornier over the years! Some guy we'll call "Adam" pointed out that the empty An-24 outweighs a full Embraer so how could I call it a fair comparison? Several months ago I was watching the American Version of "Top Gear" with my son and they had a challenge, "Cobra versus Viper" which pitted an AH-1 helicopter with infrared beam against a Dodge Viper. Well Adam, the Cobra can fly and the Viper can't but it was still a lot of fun to watch! (And the Cobra did tag the Viper three times before he made it across town.) So, I hope you enjoy these head-to-head challenges and sure enough, you may find some aircraft you want to add to your own hangar.

I already have a couple of these Head-2-Head Challenges ready to go but a couple of you asked what .air files or .cfg settings I was using on my turboprops. I can tell you that I really don't know; I have a hangar full of planes and simply unzip them as needed. I'd have to go back into the download area of FlightSim.Com and look them up again to find that information and more than likely, you all can figure that out just as well as I can. However, since the question came up about the .cfg files, this feature addresses a couple of those points.

In the late 1960's American Airlines began asking for a 250 passenger, wide-body, medium-range airliner that could operate from most existing airports. The resulting head-to-head competition between the Lockheed and Douglas (McDonnell Douglas) companies may mark (to my recollection anyway) the first time in aviation history that two companies, working in separate factories, built (for all intents and purposes) the same aircraft. I have never read any reports about the sharing or stealing of information yet the similarity in design and function of these two aircraft is remarkable.

Although the L-1011 boasted a better power-to-weight ratio and better efficiency, early powerplant problems resulted in initial delivery delays and ultimately the slightly larger, slightly heavier, longer-range, "less-advanced" DC-10 sold nearly twice as many airframes as the L-1011. The DC-10 first flew 29-Aug-70; The L-1011 on 17-Nov-70; twins born at basically the same time. The last L-1011 was completed in 1984 while the final DC-10 rolled off the production line in December 1988; however changes and retro-fits for FedEx continue to keep the DC-10s flying to this day.

So, I downloaded and installed FSX-compatible DC-10 and an L-1011 aircraft as well as several repaints for each. You all should know that everything in my hangar is freeware and not necessarily designed specifically for FSX. Here is today's challenge:

• With plenty of gas and a 50,000-pound payload we'd fly 2,300 miles from Troutdale Oregon to Wheeler Army Base in Hawaii.
• Troutdale is a GA and business airport with a 5,400-foot runway.
• Wheeler is at 837 feet ASL and has a 5,600-foot runway.

I loaded the DC-10 and departed into the rising sun. With lots of elevator trim and moderate back pressure I was able to rotate just in time (pictures above)! I cruised at only 29,000 feet and arrived into Oahu in the mid-morning. Landing and slowing without any braking was easy and I parked up having burned 77,057 pounds of gas.

Next I loaded the L-1011 in the same fashion and departed Troutdale. The improved thrust-to-weight ratio they aren't kidding about because I rotated with a good thousand feet of runway left and was blasting through my 250 knot barrier before the flaps were fully retracted (pictures below, left and center)! I set the autopilot and quickly climbed to FL290 for the cruise to Hawaii. Seven hundred-fifty miles short of the islands I was out of gas and falling from the sky!

At this point my article became about how to tweak the aircraft .cfg files to better meet your personal flying needs. Now as I stated earlier, I'm not here to bash designers or those who spend too much valuable time giving the rest of us free stuff to play with; their efforts are nothing short of generous and self-sacrificing. But sometimes I have to wonder if any testing was done at all. If nothing else, perhaps this feature will become a venue for some pre-release beta testing of freeware models.

I really am not in a position to write a technical "How To ..." article on this topic because I'm really not that knowledgeable and I'm quite sure that there have been other, more appropriate articles written in the past. But, I'm not afraid to make little tweaks to the aircraft.cfg file to meet my needs either; and in this case, I needed more range out of the L-1011. According to the paperwork, both aircraft should fly about 3,500 to 4,000 miles with "normal" load factors. According to my math on the DC-10 flight I had just done, the range would have been just over 4,000 miles. So, I went into the aircraft.cfg file and scrolled down to the Engine and Fuel Flow data. There should be an entry there called "Fuel Flow Scaler" with a number listed. The DC-10's number was 0.85000. This means that the plane will burn fuel 85% fast. (It's not a proper use of language I know but hang with me.) I wanted to burn a little more fuel and have a little less range so I set that number to 0.90000. Now I'll burn gas 90% fast, just a little faster than originally programmed. Next I accessed the fuel setting in the .cfg for the L-1011. It said, "Fuel Flow Scaler = 1.0000" meaning it was burning fuel at 100% speed. Since I only made it 2/3 of the way to Hawaii I needed to boost the range at least 35% so I set the number to 0.60000. Now the L-1011 would burn fuel only 60% fast - giving me greater range.

As I played with the gas settings I began thinking about the rocketship factor I had experienced out of Troutdale. In the same area of Engine and Fuel data in the CFG there is a setting for "Static Thrust" with the number which is the pounds of force per engine. I decreased that about 6% for the L-1011. (I was recently watching some video about Texas Turbine jet engines for Cessna Caravans and I've tweaked the static thrust of the default Caravan for better performance. Now I can take off from truly short runways; I can cruise at ALMOST 200 knots and still land at around 80 knots in under 1,000 feet. It's great!)

With the .cfg changes in place I loaded an Eastern Airline livery and repeated the flight. I still got airborne in 5,000 feet even with the 50,000-pound payload - that was better than the DC-10. Now I was able to get the gear and flaps up according to placard speeds while holding the N1 at 93%. I set the autopilot as I had done before and climbed up to FL290 but my speed was dropping. The autopilot only holds 90% N1 and with the decreased thrust it was a struggle to reach that level. Well, many times the older airliners had to do a "step-climb" and cruise at a lower level until some of the gas was burned off so this seemed reasonable to me. With the speed dropping to near stall speed I took over manual throttle and set it at 97% N1 and was able to reach 29,000 feet reasonably well. Eventually I reached Mach 0.70 and could have climbed higher had I not been doing "scientific research" for you all.

The approach and landing into Wheeler Field was slower and easier in the L-1011; it's a very nice-flying, stable machine. (You can see from the screen shot above left that I was, in fact, nose-high and probably too slow for a "good" approach; see pictures above center and right). Even so, I had burned twice as much gas as the DC-10 and a quick bit of math showed that my .cfg tweaks gave the L-1011 an improved range up to about 2,700 miles. So I went back into the Fuel Flow Data section of the .cfg and changed my 0.60000 to 0.45000. That should be about right. I figured with these changes I should have a more realistic match between these fraternal twins.

Having made these tweaks I wanted to confirm my settings so I loaded up a 1,600-mile flight from La Paz to Rio and put in 75,000 pounds of weight in each aircraft to test their ability to take off from 13,300 feet ASL and at the other end we'd land at the smaller, Santos Dumont airport.

The DC-10 just barely was airborne before the numbers but still manageable (pictures above). Cruise was uneventful and we landed smoothly and had no problems stopping (below, left and center). Some quick math showed the fuel burn range to be 2,280 miles. It looked like the DC-10 was pretty close, maybe one little tweak for fuel flow. (I'm thinking 0.88000.)

I loaded the same flight and heavy load for the L-1011 and was sweating bullets trying to get the thing airborne (picture below, left)! I pulled up the gear and tried to hold just 100-200 fpm of climb but despite my best efforts I was dropping - with the gear still retracted! I think I shaved the top off the VOR which is about 2.5 miles from the end of the runway but then I started a very gradual climb out over Lake Titicaca. Finally I was through 18,000 feet and holding 200 knots. I turned on autopilot for the rest of climb up to the cruise portion of flight.

Five minutes later I checked back on the PC to notice the stall horn blaring and that I was at 150 knots falling back through 19,000 feet. I quickly disconnected Otto and took manual control back and hand flew the beast up to FL290. I guess my pulling the power back 6% was too much so I went into the L-1011's .cfg and added 2% back to the thrust settings. I again enjoyed my approach and landing into Rio and calculated my L-1011 range at 2,419 miles with the heavier load and high-altitude departure with difficult climb (pictures, below). That is pretty darn accurate for the fuel flow numbers now. (I could probably get by with a setting of 0.47000.)

So now, here we are pages into this challenge and no clear-cut "winner" has been noted. I'm sure some features will just go like this. If this were simply a "review" I'd have to say that the L-1011 was initially presented as quite poorly done and should be avoided. However, I hope that instead this "challenge" has been both helpful and inspiring. Next time I will take my turboprop commuters to Nepal and see which one can perform there.

Ron Blehm
pretendpilot@yahoo.com