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fs3tofs9
12-19-2004, 02:14 AM
With the recent release of the DreamFleet 727, I’m sure many fellow simmers are busy right now learning the ins and out of this bird.

Unfortunately, I could not locate runway takeoff length data. So I measured and compiled the following data specific to the DreamFleet 727-200 Cargo. The data will probably be similar for the DreamFleet 727-200 Passenger.

The data should be useful because it points out something I suspected. Depending on the plane’s weight and weather conditions, at 2.0 EPR this bird could soar like an eagle or smoke along the runway chewing up thousands of feet in pavement. For example, at sea level this bird can take off in approx. 3000 ft lightly loaded in crisp weather with a strong headwind. A few months later during the still, hot summer and heavily loaded down with cargo, you’ll need about 9000 ft. If you add a safety margin of 2000 ft, you’re talking about the need for a sizable runway.

If you’re operating the freighter into small regional airports with their shorter runways, you’re going to really need to pay attention the runway length data. You’re flight could get off to a very disconcerting start if you end up flirting with the end of the runway during the takeoff roll.

I’ll upload the data to the avsim library in a better format but for now I though I would just post it below in text format.

Please provide feedback regarding suspect data or suggestions on measuring and compiling the data differently. I'll probably have another go at it using EPR = 1.8.

************************

For all data: flaps = 15 degrees, takeoff thrust = 2.0 EPR, pressure = 29.92 at sea level.

The following takeoff length data was measured using the normal rolling takeoff method, where the aircraft was started in aligned position at the beginning of the runway with thrust at idle. Thrust was then set very briefly at 1.4 EPR and then steadily advanced until takeoff power of 2.0 EPR was achieved. The takeoff length was measured when the main gear left the ground. Thus, you will need to add your desired safety margin (e.g., an additional 2000 ft.) to any takeoff length taken from the following tables.

**RUNWAY TAKEOFF TABLES 1 AND 2**
Tables 1 and 2 are zero wind (see Table 3 for headwind correction).
The ROWS are takeoff weight in 1000 LB
The COLUMNS are outside air temperature (“OAT”) in Celsius/Fahrenheit
Each table ENTRY is the takeoff runway length at the specific weight and outside air temperature.

Table 1: Elevation = 0 ft.

OAT C/F.-10(14)..0(32)..10(50)..20(68)..30(86)..40(104)..50(122)

Weight
K-lbs
110...... 3400....3500...3600....3600....3700....3700.....3800
120.......3800....3900...4000....4100....4200....4300.....4300
130.......4300....4400...4500....4600....4600....4700.....4800
140.......4900....5000...5000....5100....5200....5300.....5400
150.......5500....5600...5700....5700....5800....5800.....5900
160.......5800....5900...6000....6100....6200....6300.....6400
170.......6400....6500...6700....6800....7000....7100.....7200
180.......7500....7600...7900....8100....8200....8400.....8800
190.......8000....8100...8500....8600....8900....9100.....9300

Table 2: Elevation = 2000 ft.

OAT C/F.-10(14)..0(32)..10(50)..20(68)..30(86)..40(104)..50(122)

Weight
K-lbs
140.......4900....5000....5100....5200....5200....5400....5500
150.......5500....5600....5700....5800....5800....5900....5900
160.......5900....6000....6300....6400....6400....6500....6500
170.......6500....6600....6700....6900....7400....8100....8500
180.......8600....8700....8800....9000....9100....9400....9600

**HEADWIND CORRECTION FOR TAKEOFF LENGTH**
For the expected headwind (or tailwind when listed as NEGATIVE), ADD the correction length in feet to the runway takeoff length determined in tables 1 or 2.

Table 3: Based on a Temperature of 30 C (86 F) at Zero Feet Elevation.

Correction (ft):...+1300..+1100..+800..+400..0..-300..-500..-700..-900

BACKGROUND DATA:

Table 4: List of Assumed Dew Points for Each Temperature (OAT) used in Tables 1-3 above.

OAT (F):.........14..32..50..68..86..104..122
Dew point(F):..40..40..45..50..55..60...65

Table 5: Rotation Speed (Vr) Used for each Takeoff Weight Listed in Tables 1-3 above.

Weight (K-lbs):..110..120..130..140..150..160..170..180..190
Vr (kts):...........105..111..117..123..128..133..138..143..148

Paul Golding
12-19-2004, 12:47 PM
I hope I'm not being stupid here, but how do you measure the takeoff roll?

fs3tofs9
12-19-2004, 02:56 PM
Questions about methodology are good questions. :-) Basically, I used a brute force method of trying to do the same thing over and over again consistently but hey, my exams have finished and I like this aircraft, so what better way to decompress? ;-)

First, I obtained the desired test weight by adding weight through the F1 config. manger and fuel through the FS9 aircraft menu.

At the desired weight, I positioned the aircraft at the beginning of the test runway and checked to see if I had proper CG and trim. If so, I noted Vr and saved a situation under clear weather at 14 F temperature and 40 F dew point.

I then tried to go through a consistent throttle up procedure stopping briefly at 1.4 EPR and then advancing to 2.0 EPR.

I rotated at the set Vr speed and when I thought I was airborne and that I had performed a consistent throttle advance/rotation procedure, I hit the “pause” button but kept the same pressure on the elevator. With my other hand I would shift to spot view to verify whether the mains had just left the ground. In cases where I switched views too early and the mains had not left the ground, I would resume from pause in spot view. Because I still had the approx. same pressure on the elevator, the aircraft would continue its rotation mostly undisturbed. Then when I saw the mains leave the ground, I hit “pause” again.

When I had verified that the aircraft’s main gear had left the ground in the “paused” spot view as discussed above, I then switched to the overhead map view. I used add-on scenery with the more prominent 1000 ft signs at the side of the runway that also seemed fairly accurate, definitely within the 100 ft margin of error I was using. For example, I used FlyTampa’s 28R at KSFO for the elevation = zero tests. In the map view, you can determine within the 100 ft margin of error what position you are at between the signs and thus how many feet of runway you had left when the mains left the ground (e.g., about 3/10 after the 6000 ft sign and before the 5000 ft sign, i.e., 5700 feet to go). Once I obtained this “feet to go” figure, I subtracted it from the runway length to obtain the takeoff distance.

After getting data for the first 14 F temperature, I would reset the saved situation and rerun for the other temperature and dew point combinations. Once I had all the temperature data at a given weight, I would start over and build a new situation at the next test weight using the same procedure above.

The biggest potential source of error seemed to be the throttle advance and rotation procedure. I tried to be as consistent as possible but even small inconsistencies significantly affected takeoff distance. If I felt the takeoff roll was too inconsistent, I would do it over. Nonetheless, I would not be surprised if some data exceeded a 100 ft margin of error due to takeoff procedure inconsistency. However, since the takeoff data reflects the point where the mains leave the ground, anyone who uses it definitely needs to add their desired safety margin (e.g., if you want to see if you can take off on that 7500 ft runway, make sure the data says you can do it in 6000 ft).

skeating
12-20-2004, 10:08 PM
Could you please explain what the Dew Point has to do with any of the above and how do you get a Dew Point higher than the temperature?

fs3tofs9
12-20-2004, 11:41 PM
I think the relationship between temperature and dewpoint indicates how much water is in the air (e.g., a small difference means the air is almost saturated with water). Air saturated with water is less dense than dry air at the same temp. Less dense air reduces lift, drag, and jet engine thrust.

Here's a good link:

http://www.aerospaceweb.org/question/atmosphere/q0046b.shtml

I think you're on to something about the dew point being higher than temperature. That would mean higher than 100% humidity, which doesn't seem possible.

I'll probably redo the two lower temperatures. The 40 F dew point assumption for a 32 F was not too far off, so I don't think that will throw the length numbers outside the margin of error I was dealing with anyway. However, the 40 F dew point assumption for a 14 F temperature might have a noticable effect. Fortunately, both assumptions were for too high of a dewpoint, which would tend to make the takeoff length longer than actual (i.e., an error on the conservative side). Thanks for the feedback, appreciate it. :-)

fs3tofs9
12-20-2004, 11:44 PM
Thanks for the info.

FS9 asks for the dewpoint in Farenheit. ;-)

metro752
12-21-2004, 01:43 AM
You can only have a 40 degree dewpoint with a 14 degree temperature on paper, and even then it is wrong.

The highest the dewpoint can be is the current temperature, or it is wrong/in error.

http://www.fsuniverse.com/meyer/above/top/secret/black/aircraft/meyer_sig.jpg

Ronfreimuth
12-21-2004, 04:21 AM
>Air saturated with water is less dense than dry air at the
>same temp. Less dense air reduces lift, drag, and jet
>engine thrust.
>
>
>I'll probably redo the two lower temperatures. The 40 F dew
>point assumption for a 32 F was not too far off, so I don't
>think that will throw the length numbers outside the margin
>of error I was dealing with anyway.

I don't think FS Dew Point has any effect on air density or powerplant performance. I know it had no effect on reciprocating engines in an earlier FS version. Which are more sensitive to humidity than turbines.

Dew Point does affect the dynamic Weather in FS9. That's the only effect I'm aware of.

BTW, AFSD can be used to get exact distance from a zero point. In ft or nm. Further I've gone to 1/2 X or less when near rotation speed so I could Pause more accurately.

Ron

Gregory
12-21-2004, 11:01 PM
Good work on collecting the field length data. I have a detailed FM chart titled Boeing 727 OM - Takeoff Performance. It is believed to represent the JT8D-17 equipped jet. Ron has asked me to look at the chart and possibly characterize it.. that is come up with some formulation.

Meanwhile your numbers are interesting and I've clipped them out to a txt file. Will be comparing above data to the chart and reporting back. The scanned OM TP (nomograph style) is 900x1200 x16 gray PNG. Not sure if it should be posted here but is certainly available.

-Gregory

p.s. FD has been texted at MMMX (Mexico City, EL +7,341 ft.)
where TO roll was very close to RL for various GWs.

MTB
12-21-2004, 11:16 PM
I've worked out a set of formulas that appear to come pretty close to calculating the takeoff performance of the -200. I've got them in an excel spreadsheet which lets you input:
- Weight
- Pressure Altitude
- EPR
- Temp

- Accelerate / Stop distance (runway distance traveled from 0 to V1 plus distance to stop based on 2 engine reversers and brakes)
- Takeoff Run distance (distance traveled from stopped to an altitude of 35 feet)

The formulas appear to be correct within 1-2% for most typical conditions. Gregory - I'd really like to compare against the table you have if that's possible. Once I'm done I'll make the spreadsheet available to those who are interested.

Mike

fs3tofs9
12-22-2004, 01:13 AM
I would like to take a look at that chart. I've seen other data posted or referenced recently in the forum like a 727 Eastern checklist and a 727 FedEx (?) operations manual, so I believe it would probably be ok to post it but I'm not sure. It would be interesting just to see how they presented the data. Thanks!

fs3tofs9
12-22-2004, 01:30 AM
Good job working out the formulas. The stop distance sounds very interesting. Do you think it would be possible to also calculate stop distances for typical landing speeds?

With both real operation charts and formulas based on actual FS9 performance to work from, it could be possible come up with some great predictive data based on all sorts of altitudes, EPRs, and temps. Hello U.S. mountain and desert west. ;-)

The 727 seems really interesting in that under some conditions it gets off the ground quickly but under other conditions it will require very long runways. I don't know if modern passenger jets are more consistent short field performers but the potential for the 727 to burn you if you don't have a handle on expected takeoff length makes the plane interesting (and so to takeoff performance charts to help you deal with it).

Gregory
12-22-2004, 09:25 AM
>I would like to take a look at that chart. I've seen other
>data posted or referenced recently in the forum like a 727
>Eastern checklist and a 727 FedEx (?) operations manual, so
>I believe it would probably be ok to post it but I'm not
>sure. It would be interesting just to see how they
>presented the data. Thanks!

Here's a look at the chart reduced more than 50% for preview.

http://mywebpages.comcast.net/flightsim/727_TAKEOFF_PERFORMANCE_435x580.gif

In the lower left corner is Field Length (5,000-14,000) with three adjust factors; runway slope, head-tail wind, and flap position. You can see increasing EPR contours above that. The center section has PA (pressure altitude) correction slopes which I believe means field elevation. The PA lines are negative and rather steep. To the right is OAT derate and to the extreme right is `Field Length Limit' in kg (ft) which is basically GTW.

You can always work backwards from right to left starting with GTW. :)

If you'd like a full size image.. send email to gabbeyATdynanetDOTcom and I'll forward.

-Gregory

Gregory
12-24-2004, 11:42 AM
>I could not locate runway takeoff length data.
>So I measured and compiled the following data specific
>to the DreamFleet 727-200 Cargo. The data will probably be
>similar for the DreamFleet 727-200 Passenger.
>
>Table 1: Elevation = 0 ft.
>
>OAT
>C/F.-10(14)..0(32)..10(50)..20(68)..30(86)..40(104)..50(122)
>
>Weight
>K-lbs
>110...... 3400....3500...3600....3600....3700....3700.....3800
>120.......3800....3900...4000....4100....4200....4300.....4300
>130.......4300....4400...4500....4600....4600....4700.....4800
>140.......4900....5000...5000....5100....5200....5300.....5400
>150.......5500....5600...5700....5700....5800....5800.....5900
>160.......5800....5900...6000....6100....6200....6300.....6400
>170.......6400....6500...6700....6800....7000....7100.....7200
>180.......7500....7600...7900....8100....8200....8400.....8800
>190.......8000....8100...8500....8600....8900....9100.....9300
>
>Table 2: Elevation = 2000 ft.
>
>140.......4900....5000....5100....5200....5200....5400....5500
>150.......5500....5600....5700....5800....5800....5900....5900
>160.......5900....6000....6300....6400....6400....6500....6500
>170.......6500....6600....6700....6900....7400....8100....8500
>180.......8600....8700....8800....9000....9100....9400....9600
>

Here are your numbers overlayed on the TO Ops Manual contours
formulated in Excel spreadsheet. The xls file was made from the
Boeing 727 OM table as seen in this thread.

http://mywebpages.comcast.net/flightsim/722_TO_data.png

If you'd like to experiment with the SS (spreadsheet).. it should
come up in MSIE if your OS has the required components. Head/
tail winds and runway slope are not included as yet.

http://mywebpages.comcast.net/flightsim/727-200_Takeoff_Performance_v04.xls

-Gregory

ex- Bendix, Northrop, Lockheed Martin engineer

Ronfreimuth
12-24-2004, 06:13 PM
>I've worked out a set of formulas that appear to come pretty
>close to calculating the takeoff performance of the -200.
>I've got them in an excel spreadsheet which lets you input:
>- Weight
>- Pressure Altitude
>- EPR
>- Temp
>
..........
>
>The formulas appear to be correct within 1-2% for most
>typical conditions. Gregory - I'd really like to compare
>against the table you have if that's possible. Once I'm
>done I'll make the spreadsheet available to those who are
>interested.
>Mike

Mike,

Please cc: anything you send to Greggory to me also. I've been looking at his preliminary TO SS's for the 727. He also did a lot of flight testing and plotting some months ago.

ron.freimuth@att.net

Rolling friction is high in MSFS, however I've done some tests that indicate a neglible effect on TO distance as long as TO thrust is nominal. Full Reverse thrust plus excess rolling friction was set to what a 727 FM Sim gave.

Strider3
01-10-2005, 10:07 PM
I think it should be pointed out that the MORE "water" (humidity) in the air the MORE dense it is...not vice-versa, and, as your link stated, denser air results in better combustion turbine efficiency (due to the increased amount of air the compressor sections can "move" into the combustors). More air = more fuel = more power (in simple terms).

I run 4 G.E. 7EA combustion turbine generators at our power plant. On cold and high humidity days output can run as high as 80 megawatts on each unit. On a hot, dry day it can drop to 68 Megawatts. That's quite a loss."Cold and dry" or "Hot and humid" days fall somewhere in between. In summer we actually spray a fog of water into the CT inlet ducting...to increase efficiency by adding "density" to the air...in the form of water (humidity).

I'll look for the GE temperature, pressure and humidity charts from the GE manual, if anyone's interested. It has no bearing on the lightweight Aircraft "jet" engines, as far as output numbers, but ALL combustion turbines will see an improved efficiency with "wet" or cold air.

And Lift will increase with denser air...but I believe Drag will also increase. I would hazard the guess that the Lift will improve much more than the Drag, in denser air...and thus a shorter take-off run?

Strider3
01-10-2005, 10:20 PM
This may help explain the term "Pressure Altitude":

http://www.csgnetwork.com/pressurealtcalc.html

And it comes above a handy "pressure altitude" calculator.

Gregory
01-11-2005, 09:57 PM
thanks gr.. a handy calc!

More emails are coming in requesting the TO sheet.. and for some reason I'm becoming paranoid and asking `where are you located' and that sort of thing. So a link is provided below to retrieve the chart directly. Still ok to send emails on flightsim however. :)

mywebpages.comcast.net/flightsim/727_TAKEOFF_PERFORMANCE.png (215k)

-Gregory

fs3tofs9
01-15-2005, 01:37 PM
Wow, DreamFleet sure did a good job. Look's like their 727's takeoff performance matches real world data. The variance at the longer runway lengths was probably due to measuring error on my part, tending to increase as the runway length increased.

Very interesting data, thanks!

Strider3
01-18-2005, 12:45 AM
Gregory,

In the example calculation, on your chart, from the "flap position" area the calc line continues on to the "average takeoff EPR area. It appears to stop at "2.125" EPR. What is "average takeoff EPR" and how was it come by, in the example?

Thanks!

PhilipsCDRW
01-18-2005, 02:52 AM
This is a very helpful thread! Thanks for collecting and compiling this data, it is much appreciated, I'm printing it now and will add it to the appropiate manual section.

Gregory
01-19-2005, 01:51 AM
>Gregory,
>
> In the example calculation, on your chart, from the "flap
>position" area the calc line continues on to the "average
>takeoff EPR area. It appears to stop at "2.125" EPR. What is
>"average takeoff EPR" and how was it come by, in the example?
>
> Thanks!

The example `calc line' was there already when the file arrived. I've cleaned up the chart, sharpened it, etc. for best clarity and moderate filesize. Someone has apparently plotted the trace up to EPR=2.125 which serves to demonstrate typical use. Not an expert here but `Ave EPR' probably means if you ran the takeoff five times.. that would be the likely value.

Keep in mind the chart is useful to optimize your takeoff by `trading off' one parameter for another. Use the Max TO EPR chart for takeoff EPR setting. Then see how it `plays' into the takeoff scenario. Best to ask someone who knows what they're talking about! :)

Have fun with your Boeing Sim.

-Gregory

metro752
03-18-2005, 10:12 AM
Yes, I thought that maybe was a typo earlier, and he meant 14/14

Anywho, who measures the dewpoint in aviation in Farenheit.

University of Illinois Champaign Urbana
http://ww2010.atmos.uiuc.edu/(Gh)/guides/maps/sfcobs/dwp.rxml

"When the dew point temperature and air temperature are equal, the air is said to be saturated. Dew point temperature is NEVER GREATER than the air temperature. Therefore, if the air cools, moisture must be removed from the air and this is accomplished through condensation. This process results in the formation of tiny water droplets that can lead to the development of fog, frost, clouds, or even precipitation."

EDIT: To be a bit more accurate, you could have used LAT/LON coordinates to figure out exact distances.

http://www.fsuniverse.com/meyer/above/top/secret/black/aircraft/meyer_sig.jpg