DC-9 -15 Performance..

[macs]

Hi,
No criticism, just an observation:
While flying today, I noticed an exaggerated performance for the DC-9 -15 using the JT8D-5's (See pic).



The picture actually does not show the worst part where at about FL190, I was getting a sustained climb rate of about 4000 fpm @ 300 KIAS and. with about 1.78 EPR.
Also, it was impossible to go more than about 1.78 EPR on the engine as I had run out of throttle travel (Well, not that I needed any more, I was just trying to use the max EPR for recommendation shown on the RAT). The atmosphere was a bit hotter than standard, but not much on this occasion, so temperature did not play I role I believe.
I checked my joystick calibration and it was good.
I have checked that the right models are paired together as explained. Here are the base packages I have:

- hjg mcdonnell douglas dc-9-10 jt8d-5 v1.13
- hjg dc-9-10 jt8d-5 panel v1
-alm_dc9-15_pj-dnc_1974 (This one is irrelevant as it is a texture)
-hjg_dc9-panel-core-files v1

Just curious if I had made a mistake somewhere.

Regards,
Macs

[aerofoto - HJG Admin]

No criticism, just an observation

No problem MACS

I did a lot of testing with the JT8D-5 DC9-10 base pack and panel .... as I have with each of these panels prior to release (to learn how to fly them best) and which is partly why it took us so long to get them released.

I make no claim that what we have/offer is "PERFECT" (FS itself far from perfect of course) .... but .... my own flight testing of this engine/aircraft version resulted in the following conclusions which then became my recommended procedures for flying this particular engine/aircraft type ....

DC9-10 (P&W JT8D-5)

2X P&W JT8D-5 fanjet engines rated at 12,250 LBS thrust e/a

MGTOW = 81,800 LBS

FUEL & PAYLOAD

LEFT = 83.2%
CENTER = 80.5%
RIGHT = 83.2%
No payload adjustment .... results in 16 LBS overload

PANEL = "DC9-10 JT8D-5"

TRIM = 5.0 units (gauge indication)
FLAP SETTING = 15*
MAX T/O THRUST = 1.80 EPR
FLAP 15 RETRACT SPEED = 200 KIAS
FLAP 5 RETRACT SPEED = 220 KIAS
FLAP/SLAT RETRACT SPEED 230 KIAS
AFTER T/O CLIMB THRUST = 1.65 EPR

Maintain 2,000 FPM ROC until after gear and flap retraction .... then increase ROC to 3,000
FPM and assume the following climb schedule ....

- Maintain 3,000 FPM ROC until 10,000 FT
- 10,000 FT reduce ROC to 2,500 FPM
- 14,000 FT reduce ROC to 2,000 FPM
- 16,000 FT reduce ROC to 1,800 FPM
- 18,000 FT reduce ROC to 1,500 FPM
- 20,000 FT reduce ROC to 1,200 FPM
- 22,000 FT reduce ROC to 1,000 FPM
- 24,000 FT reduce ROC to 750 FPM
- 26,000 FT reduce ROC to 500 FPM
- 28,000 FT reduce ROC to 250 FPM
- 31,000 FT ALT CAPTURE

FL250 CRUISE PERFORMANCE

94 mile climb to FL250

IAS = 327
MACH = 0.76.9
EPR = 1.65
N1 = 88.0%
EGT = 453
N2 = 90.8%
F/F = 3,202 LBS (X2)

FL280 CRUISE PERFORMANCE

climb to FL280 exceeds 194 miles

IAS = 315
MACH = 0.78
EPR = 1.66
N1 = 90.3%
EGT = 449
N2 = 92.7%
F/F = 3,032 LBS (X2)

FL310 CRUISE PERFORMANCE

climb to FL310 exceeds 194 miles

IAS = 306
MACH = 0.80
EPR = 1.68
N1 = 94.1%
EGT = 449
N2= 96.2%
F/F = 2,956 LBS (X2)

N.B. FL250 to FL280 is quite sufficient cruising altitude for this lighter MGTOW and less powerful DC9-10 version.

The above performance is what you should be seeing/getting at or near MGTOW .... and following my own profile.

I've never .... ever .... set or been able to sustain a 4,000 FPM ROC at any time with this aircraft (or any of our DC9's) and as my above notes should indicate.

A 3,000 FPM ROC .... "YES" .... but .... only after "clean-up" and after-T/O thrust reduction from EPR 1.80 (the maximum SL 15*C JT8D-5 value) to EPR 1.65 (I've never recorded the N1/N2 turbine values here and which are much more relevent) .... and only up to 10,000 FT.

If you can get this aircraft to climb at 4,000 FPM .... at the altitude you state .... and with a near full load too .... then "good for you"

"IF" you're concerned about possible "over-performance" (which is the case .... if I'm understanding you correctly) then you should check that you are indeed using the JT8D-5 base pack/FDE which you understand to be in use with this aircraft panel. Check the top/header on each CFG file .... because in every case I've also stated the aircraft/engine type details there.

The JT8D-5 powered DC9-10 has the lowest engine thrust rating (12,250 LBS X2) among our entire DC9 family, but then, it also has the lowest MGTOW (81,800 LBS) among our DC9 family too .... being quite a bit lighter that the 85,700 LB MGTOW JT8D-1 and 90,700 LB MGTOW JT8D-7 versions !

Beyond "THIS" .... the measured thrust and fuel flow values (as per my notes) are "about" what they should be for this particular DC9 engine/aircraft type .... as well as our others too .... according to the data we sourced !

Mark C
AKL/NZ

[aerofoto - HJG Admin]

I note you appear to be flying ALM DC9-15 PJ-DNC.

Allow me then to assist you by recommending a better/more accurate engine/panel choice for your selected DC9-15 ....

PJ-DNC was originally PH-DND, delivered to KLM during August 1966. ALM acquired it around 1970. This aircraft was originally built as a JT8D-1 powered aircraft .... but .... "may" have been upgraded to JT8D-7 powerplants (as many were) by the time it flew for ALM. Both JT8D-1 and D-7 engines are certified for the same power rating .... 14,000 LBS thrust.

Either the JT8D-1 or JT8D-7 aircraft base pack/panel combinations would be your best choice for this airline/aircraft .... assuming you want to fly for authenticity.

Here's my DC9-10/15 performance notes/observations for both versions ....

DC9-10 (P&W JT8D-1)

2X P&W JT8D-1 fanjet engines rated at 14,000 LBS thrust e/a

MGTOW = 85,700 LBS

FUEL & PAYLOAD

LEFT = 87.3%
CENTER = 80.5%
RIGHT = 87.3%
No payload adjustment .... results in 7 LBS overload

PANEL = "DC9-10 JT8D-1"

TRIM = 5.0 units (gauge indication)
FLAP SETTING = 15*
MAX T/O THRUST = 1.98 EPR
FLAP 15 RETRACT SPEED = 200 KIAS
FLAP 5 RETRACT SPEED = 220 KIAS
FLAP/SLAT RETRACT SPEED 230 KIAS
AFTER T/O CLIMB THRUST = 1.75 EPR

Maintain 2,000 FPM ROC until after gear and flap retraction .... then increase ROC to 3,000
FPM and assume the following climb schedule ....

- Maintain 3,000 FPM ROC until 10,000 FT
- 10,000 FT reduce ROC to 2,500 FPM
- 14,000 FT reduce ROC to 2,000 FPM
- 16,000 FT reduce ROC to 1,800 FPM
- 18,000 FT reduce ROC to 1,500 FPM
- 20,000 FT reduce ROC to 1,200 FPM
- 22,000 FT reduce ROC to 1,000 FPM
- 24,000 FT reduce ROC to 750 FPM
- 26,000 FT reduce ROC to 500 FPM
- 28,000 FT reduce ROC to 250 FPM
- 31,000 FT ALT CAPTURE

FL250 CRUISE PERFORMANCE

94 mile climb to FL250

IAS = 329
MACH = 0.77
EPR = 1.80
N1 = 82.4%
EGT = 437
N2 = 86.6%
F/F = 3,382 LBS (X2)

FL310 CRUISE PERFORMANCE

climb to FL310 exceeds 194 miles

IAS = 306
MACH = 79.5
EPR = 1.83
N1 = 85.6%
EGT = 423
N2= 88.7%
F/F = 3,070 LBS (X2)

DC9-10 (P&W JT8D-7)

2X P&W JT8D-7 fanjet engines rated at 14,000 LBS thrust e/a

MGTOW = 90,700 LBS

FUEL & PAYLOAD

LEFT = 88.5%
CENTER = 80.9%
RIGHT = 88.5%
No payload adjustment .... results in 19 LBS overload

PANEL = "DC9-10 JT8D-7"

TRIM = 5.0 units (gauge indication)
FLAP SETTING = 15*
MAX T/O THRUST = 1.98 EPR
FLAP 15 RETRACT SPEED = 200 KIAS
FLAP 5 RETRACT SPEED = 220 KIAS
FLAP/SLAT RETRACT SPEED 230 KIAS
AFTER T/O CLIMB THRUST = 1.75 EPR

Maintain 2,000 FPM ROC until after gear and flap retraction .... then increase ROC to 3,000
FPM and assume the following climb schedule ....

- Maintain 3,000 FPM ROC until 10,000 FT
- 10,000 FT reduce ROC to 2,500 FPM
- 14,000 FT reduce ROC to 2,000 FPM
- 18,000 FT reduce ROC to 1,800 FPM
- 20,000 FT reduce ROC to 1,500 FPM
- 22,000 FT reduce ROC to 1,200 FPM
- 24,000 FT reduce ROC to 1,000 FPM
- 26,000 FT reduce ROC to 750 FPM
- 28,000 FT reduce ROC to 500 FPM
- 30,000 FT reduce ROC to 250 FPM
- 31,000 FT ALT CAPTURE

FL250 CRUISE PERFORMANCE

74 mile climb to FL250

IAS = 328
MACH = 0.77
EPR = 1.80
N1 = 82.5%
EGT = 440
N2 = 86.8%
F/F = 3,373 LBS (X2)

FL310 CRUISE PERFORMANCE

74 mile climb to 173 miles

IAS = 305
MACH = 79.9
EPR = 1.83
N1 = 85.4%
EGT = 422
N2= 88.5%
F/F = 3,050 LBS (X2)

Both aircraft performances are quite similar (in respect of what can be simulated easily within FS), but, the aircraft weights are different.

At one stage I was debating, with myself, as to whether or not we'd bother offering the JT8D-1 version .... but .... I later thought "WHAT THE HELL" .... and included it anyway .... just for the sake of the 85,700 LB MGTOW at which some DC9-10/15 series aircraft were once certified along the way to their eventually being recertified for up to 90,700 LB MGTOW.

Comming back to your JT8D-5 DC9-10/15 observations ....

Even though you've observed the lower EPR value (again turbine values are more relevent) associated with these engines .... what you're seeing there is "about right". T/O thrust for this engine should not exceed EPR 1.80 (at SL and 15*C) .... with an after T/O and cleanup thrust reduction to no less than EPR 1.65 .... then follow my ROC profile. For each of these test flights I left the power alone beyond the after T/O thrust reduction and just used the aircraft attitude to control speed .... which works really well for me. This aircraft/engine combination struggles a bit above FL250 .... so .... I wouldn't be inclined to go much higher than FL280 at the very most .... and even though it will struggle on up to FL310 after a very long climb and will cruise quite nicely at around 306 KIAS .... for the following engine related values ....

EPR 1.68,
N1 94.1%
N2 96.2%

Use any more power than is prescribed within my pprofiles and one's probably then just abusing one's engines.

Again .... FL250 is probably a better altitude for the JT8D-5 DC9-10/15 !

With all of these DC9's .... make sure you're indeed using the correct aircraft base pack/FDE and panel combinations .... or .... performance will be either impaired/enhanced outside of reality.

Mark C
AKL/NZ