Simviation

DC-10: A Pilot's Perspective

by Wayne Brown

Page 3

Please direct your attention to this paragraph for a brief but important safety announcement. The information contained in this review is not intended for use in actual flight training. It is provided for entertainment purposes only, and no guarantee is made for the accuracy of the information presented. Much of the information is subjective in nature, and results may vary significantly based upon operating system, technique, panel used, download version, modifications to air file or aircraft config file, and other factors. In the unlikely event of a sudden loss of your sense of reality, please remember that Microsoft Flight Simulator is only a game. Please do not attempt to obtain a DC-10 type rating using either the FFX/SGA DC-10 for Microsoft Flight Simulator or the information presented here. Thank you, and enjoy your flight!

***PLEASE NOTE THAT THE FOLLOWING TEST RESUTS WERE ACHEIVED USING A BETA UPGRADE TO THE ORIGINALLY RELEASED FLIGHT DYNAMICS. THE UPGRADE IS SCHEDULED TO BE RELEASED PUBLICALLY AT A LATER DATE***

ADI Attitude Director Indicator (a combination attitude indicator and flight director)

CG Center of Gravity (usually expressed as a percentage of Mean Aerodynamic Chord of the wing)

EOW Empty Operating Weight (weight of aircraft including crew, crew luggage, oil, normal service items)

fpm feet per minute (rate of climb or descent, shown on the Vertical Speed Indicator)

GW Gross Weight (usually intended to mean the current actual weight of the aircraft)

KIAS Knots Indicated Airspeed (speed as shown on the airspeed indicator, sometimes simply called "IAS")

MTOW Maximum Takeoff Weight (maximum permissible weight of the aircraft for takeoff)

*Note: Stabilizer trim setting, using Staffan Ahlberg's DC-10 panel, was +08 units nose up, equivalent to approximately 1 index mark nose up on the default elevator trim indicator. Using the correct stabilizer trim setting (based on CG position and flap setting) is very important in the real aircraft. In FS2002, it is only necessary to have the approximate correct setting, and minor differences in trim setting do not significantly affect performance. Virtually all aircraft in FS2002 seem to require a moderate amount of nose up trim, such as this setting used on the DC-10, to achieve rotation at the correct speed.

V2 196 (Takeoff Safety Speed, to be flown in event of an engine failure during takeoff after V1)

Cln M/M 286 (Clean Minimum Maneuvering Speed, i.e. speed required to exceed 15° bank with slats retracted)

V2 166 (Takeoff Safety Speed, to be flown in event of an engine failure during takeoff after V1)

Cln M/M 263 (Clean Minimum Maneuvering Speed, i.e. speed required to exceed 15° bank with slats retracted)

If done at the proper speed and rate, liftoff should occur at 10° of pitch (with main gear struts extended, tail contact occurs at 15.5°). Rotation is continued in basically a continuous, fluid motion up to a target initial climb attitude of 17.5° (maximum of 20°) to maintain V2+10 knots. V2+10 is held using pitch to 800 feet AFL (assuming Flaps 15 or less is used for takeoff), at which point the nose is lowered to a 10° deck angle, with flap and slat retraction occuring at the appropriate speeds as the aircraft accelerates. In these tests, the aircraft was able to achieve a normal rotation at the correct speed at both demonstrated flap settings. The ability to achieve an "early" rotation, i.e. approximately 10-12 knots prior to Vr speed, was also demonstrated.

Pitch attitude to hold 292 KIAS should be 9.5° nose up, resulting in 2560 fpm rate of climb. Actual pitch for sim was 15° nose up, with approximately 5500 fpm rate of climb.

Pitch attitude to hold 292 KIAS should be 8.5° nose up, resulting in 2110 fpm rate of climb. Actual pitch for sim was 13° nose up, with approximately 4900 fpm rate of climb.

Pitch attitude to hold 292 KIAS should be 7.5° nose up, resulting in 1670 fpm rate of climb. Actual pitch for sim was 11° nose up, with approximately 4200 fpm rate of climb.

The results indicate a reasonably accurate pitch attitude with somewhat better than realistic climb performance for this weight. The climb tests were focused on getting a good "snapshot look" at exact pitch attitude and climb rate at specific altitudes. With a rapid climb at a constant IAS, required deck angle (pitch) to hold desired IAS changes with altitude, as does throttle position to hold a constant N1. Multiple profiles were flown to try and ensure that a slight deviation in any given parameter wasn't affecting validity of test results in another parameter. That said, slight differences like this do not significantly detract from the sim's realism. The focus is normally on nailing speed, not vertical velocity, in a climb on the real plane... you know generally what climb rate to expect for a given set of conditions (if it doesn't seem right, you start looking for reasons why), but you don't worry about exactly what your VSI shows. Other factors, such as updrafts/downdrafts and control rigging (airplanes get bent with age, just like people) can influence the rate you'll see on the needle.

Test conditions: DC-10-30 at GW of 400,000 lbs. (36,000 lbs. fuel on board), 300 KIAS

To hold 300 KIAS, pitch attitude should be 2° nose up, with 95.9% N1 required for cruise power setting. Actual pitch was 3° nose up (very close), but only about 70.5% N1 was required.

Test conditions: DC-10-30 at GW of 500,000 lbs. (136,000 lbs. fuel on board), 300 KIAS

To hold 300 KIAS, pitch attitude should be 3° nose up, with 98.8% N1 required for cruise power setting. Actual pitch was 3° nose up (right on), but only about 72.5% N1 was required.

Test conditions: DC-10-30 at GW of 400,000 lbs. (36,000 lbs. fuel on board), 285 KIAS

To hold 285 KIAS, pitch attitude should be 2.5° nose up, with 97.8% N1 required for cruise power setting. Actual pitch was 3° nose up, with 75.5% N1 required.

A normal cruise pitch attitude is around 1° to 3° at altitude, usually never more than that unless you get way too slow. Pitch attitude will increase with weight and decrease with altitude, but it doesn't vary much. More than about a 3° deck angle would be quite noticeable in the real aircraft, but I don't feel that it is in the sim. The DC-10 is normally flight planned at around .83 Mach (a number of factors are built into the computer flight planning programs, and it may vary from about .81M to .85M). At .83M, max altitude for the DC-10-30 (with smooth air, standard temp) at 350,000 lbs. is FL410. At 440,000 lbs. it is FL370, and at 530,000 lbs. it is FL330. Longer flight segments usually call for an initial cruising altitude in the low to mid 30's, stepping up to an altitude in the upper 30's as weight is reduced. A step climb to an altitude only in the 20's is rare, and would only be done to avoid turbulence or severe headwinds in the 30's. Only with a combination of very heavy weight and very hot temperature would the aircraft be weight limited to an altitude below FL310. In any case, a normal cruise pitch attitude would be in the ranges mentioned above. Normal cruise power settings on the Series 30 are typically between 90% and 102% N1. Only at very light weights, and usually at lower cruise speeds or altitudes, would cruise power be set at less than 90% N1.

Test conditions: DC-10-30 at Honolulu (HNL), standard day (59°F), zero wind, Landing Gross Weight (LGW) 400,000 lbs. (36,000 lbs. fuel on board), Flaps 35°.

0/RET M/M 240 (Clean Min Maneuvering Speed; slats are extended before reducing below this speed)

0/EXT M/M 207 ("Zero/Extend Min Maneuvering Speed"; Flaps 22 is normally selected before reducing below this speed)

22/EXT M/M 170 (Landing Flap Setting, in this case 35°, is selected before reducing below this speed)

Vapp 156 (This is the actual final approach speed when fully configured for landing, it is normally Vref + 5, but may be adjusted up to V2 + 20 for existing wind conditions)

Test conditions: DC-10-30 at Honolulu (HNL), standard day (59°F), zero wind, Landing Gross Weight (LGW) 400,000 lbs. (36,000 lbs. fuel on board), Flaps 50°.

0/RET M/M 240 (Clean Min Maneuvering Speed; slats are extended before reducing below this speed)

0/EXT M/M 207 ("Zero/Extend Min Maneuvering Speed"; Flaps 22 is normally selected before reducing below this speed)

22/EXT M/M 170 (Landing Flap Setting, in this case 35°, is selected before reducing below this speed)

Vapp 151 (This is the actual final approach speed when fully configured for landing, it is normally Vref + 5, but may be adjusted up to V2 + 20 for existing wind conditions)

Note: Vref for the Series 30, which is based on weight and flap setting, varies from 118 knots for a Flap 50 configuration at 260,000 lbs. LGW, to 152 knots for a Flap 35 configuration at 403,000 lbs., the Maximum Landing Gross Weight (MLGW). For any given weight, using Flaps 50 instead of Flaps 35 lowers Vref by 3 to 5 knots. Once Vref is determined, Vapp (the actual approach speed, to which the orange airspeed command bug is set using the selector on the Flight Guidance Panel) is calculated by adding half the steady wind + all of the gust factor. A minimum of 5 knots and a maximum of 20 knots is added. Therefore with no wind, Vapp=Vref + 5. With, for example, winds reported as "320 at 16, gusts to 23", you would add half the steady wind (8 knots, or half of 16), plus all of the gusts (7 knots, which is the difference between 16 and 23) to arrive at a total additive of 15 knots, or Vref + 15. So, even at extremely light weights you would never have an approach speed less than 123 knots, and at MLGW and using max additives, you would normally never have a final approach speed in excess of 172 knots. However, landing under abnormal or emergency conditions above MLGW or with an abnormal flap/slat configuration would require a faster speed. Max tire speed on the DC-10-30 is 205 knots, and you would not exceed that speed except in extreme emergencies.

Under the test conditions for Flaps 35°, the aircraft should have a nose up attitude of about 2.7° while holding a final approach speed of 156 KIAS on a 3.0° glide slope, and required descent rate would be about 800 fpm. Actual pitch attitude was around 3°, very close to what it should have been. Power required to hold approach speed was approximately 70% N1, slightly lower (about 2%) than what would be expected in the real aircraft. For Flaps 50°, pitch attitude for these conditions should be about 1.7°, with power at about 82.5% N1. Actual pitch for the tests at Flaps 50° was between .5° and 1° nose up, with a power setting of about 73% N1. The Flaps 50° setting is seldom used in the real world except with short (less than 7000') or slippery runways, or with inoperative antiskid. A slightly flatter (1° to 1½°) pitch angle would be seen with a Flaps 50 landing configuration. For either flap setting, a heavier LGW would result in a higher deck angle. Basically, a stabilized final approach pitch attitude could vary from 1.5° for a Flaps 50 approach at 300,000 lbs., to 3.3° for a Flaps 35 approach at Max Design Landing Weight of 421,000 lbs. During approach, the preferred technique is to set the approximate correct pitch attitude on the ADI, the approximate correct descent rate on the VSI, and fine tune the speed and glide slope tracking with small pitch and power corrections. The aircraft is very stable, due in part to its mass. With practice, you can easily hold desired approach speed in the DC-10 within 1 knot in smooth air while tracking the glide slope with no visible deflection. The sim is much like the real plane in the flare as well. You start thinking "flare" at 50 feet RA (Radio Altitude), then at 30' you flare it much like you would a Cessna- just pull the power smoothly to idle as you increase pitch slightly, and a reasonably nice touchdown will result more often than not. Landing distance to a full stop appears to be amazingly accurate. Based on a LGW of 310,000 lbs., standard day conditions with no wind, maximum braking and full reverse to 80 KIAS, you should be able to stop a DC-10 in 2940 feet from a point 50 feet above the threshold (main gear wheel clearance over the threshold in this case will actually be around 20 feet). In repeated tests in this sim, with a LGW of 315,000 lbs. and conditions as stated above, the aircraft touched down at around 600 feet down the runway, coming to a full stop just prior to the end of the touchdown zone, a distance of about 3000 feet. Keep in mind, this is a maximum performance landing. For a normal landing, a visual aim point 1800 feet down the runway is used. This will result in a 40 to 60 foot threshold clearance and an actual touchdown point approximately 1000 to 1100 feet from the end of the concrete. Overall, the FDE approach/landing phase parameters on this aircraft are far closer to the characteristics of the real DC-10 than any I've seen in FS2002.

Test conditions: DC-10-30 in clean (0/RET) configuration, GW 440,000 lbs., wings level (0° bank angle)

Stall speed should be about 169 KIAS at this weight and configuration. Actual stall speed in the sim is slower, at 130 KIAS.

Before getting too critical of a virtual airplane's ability to match the numbers advertised for its real world counterpart, remember the old adage regarding aircraft performance: "Measure it with a micrometer, mark it with a grease pencil, and cut it with an axe". While maximum safety and precision are the real world goals, the fact remains that whether real or simulated, the world is not perfect. Real airplanes, for one reason or another, do not always perform exactly as published. Therefore, it is unrealistic to expect perfection on your desktop simulator. Overall, the tests confirm that the FFX/SGA model is an excellent representation of the DC-10. It, like every other aircraft on your flightsim menu, is not designed to reach the level of reality provided by the multi-million dollar, full-motion simulators found in airline or military training centers (which, for all their sophistication, still don't fully measure up to the feel of the actual aircraft). Instead, it is simply intended to convey a general feel for the real plane, and that is something the designers at FFX/SGA have done quite well. Many of the differences noted are due to limitations within the MSFS program, others could possibly be tweaked (at the risk of adversely affecting other characteristics), but even "as is," this sim is a lot of fun to fly...and that is what counts!

A native of Shreveport, Louisiana, Wayne began flying in 1978. He was hired at a major US airline in 1987, starting as a B727 flight engineer. In addition to the "Trimotorsaurus Rex", other aircraft flown include the B757, B767, DC9 and DC10. An ATP/CFII with glider and seaplane ratings, he is also active in general aviation.

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