IRIS C-27J Throttle and Prop problems/questions

[TacomaSailor]

I've read the other thread about the throttles, reversing, and feathering. I've made the recommended changes and have decent reverse thrust.

I frequently, but not always, have a severe imbalance between the two engines. When I started the engines this time I found for left and right:

RPM 90% 52%
ITT 735 735
N1 63 63
N2 90 52
FF 20 49
PSI 83 77

PROP SYNCH OFF
No matter how I move the throttles in the VC - the engines return to the values shown above
AND - I can not move the throttles in the VC independently

PROP SYNCH On
I can move the VC throttle independently and the prop RPMs vary with the throttles
If I move the yoke or stick throttle the prop RPMs quickly separate and change at very different rates

Other times when I start the engines the Nx and RPM values are what I would expect

I have had several flights end in disaster while on autopilot at flight levels in a stable configuration that had been maintained for a long period and suddenly there is a huge asymmetric thrust.

There is nothing I can do with the VC throttle or the yoke or the stick throttle to get the left RPM below 90% - is that normal?

Are my questions above "features" or problems?

I've made three more flights since the post above - in two of them the left engine N1 would never drop below 93% and the right engine N1 would start at 52%. With TO power applied - L engine goes to 101% but R engine only spools up to 85% N1 after 30 seconds and never gets above 90%.

I can not control that much asym thrust with the rudder pedals and can not take off!


PROP FEATHERING
The manuals says "OH-Y-1 - Left and Right Prop Control switchesManually sets the prop pitch between FEATHERED, UNFEATHERED and NORMAL, where NORMAL is controlled by the AUTOFEATHER system"

When I click on either feather control the red guard switch opens but if I touch, right click, left click or do anything else to the toggle that is exposed - the red guard just flips down and nothing else changes.

I've tried this with PROP SYNCH ON/OFF and AUTOFHR ON/OFF

HOW do I feather or unfeather the props?

Thanks for any suggestions

 

[warchild]

Youve certainly got something odd going on there.. Being turbines, engine rpm should never drop below 93%. All your throttle is doing is changing the pitch of the prop blades.. I'll run it a few times with AFSD and see what that tells me in the morning. The only possibility i can think of with those particular values appearing would be on start up, before the engines have stabilized but i'll take a look.. Other things that may come into play are random failures. If another module is programmed for creating them, it could be interfering with the systems programming.. I truly dont know though and am speculating.. Let me get a nights sleep and look into this more seriously in the morning.. }


Pam


PS.. props should feather by following the instructions in the manual as you have done. Only thing i can think of that would change that would be something like FSUIPC ( registered version ), since it has the ability to be programmed to take control of your inputs..

 

[TacomaSailor]

I use FSUIPC a lot but am 100% certain it is not enabled when I fly the C-27J

I sometimes take 30 minutes on the ramp with the engines running while trying to get the props and Nx speeds in synch. Once the problem of out of synch Nx speed occur - I have to load another AC into FSX - operate the throttles and then reload the C-27J.

SOMETIMES - the C-27J reloads with engines that operate as I would expect - but about 1/3 of the time the engines are still out of synch and operate as I describe earlier.

I suspect there are several problems with my C-27J - For example:
OVERHEATING ENGINES and STALLING


Empty AC but less than full fuel load (40,000 pounds) - standard day
Take off from Miramar MCAS and climb out at 1000 fpm - I have to keep the N1 below 93% to keep from getting a HOT engine alarm below 1000'. BUT - that requires a 6,000 foot takeoff roll and a climb rate of 800fpm at 124 knots.


The performance I see in my C-27J does not match the C-27J website ( http://www.c27j.com/essential-facts ) which says "The C-27J has outstanding threat-avoidance capabilities, including a take-off ground run of about 1,900 feet at maximum take-off weight on an unpaved surface. In a tactical environment, the aircraft is capable of climbing to 10,000 ft in 3 minutes."


Cruise at 7500' at 211 KIAS - try to climb to 10000 at 2000 fpm - HOT engines in 30 seconds N1=85% N2=100

Cruise at 9500' at 210 KIAS - try to climb to 16000 at 1400 fpm - can only maintain 180KIAS and 1800fpm to 13000'
Then KIAS and climb rates begin to decrease - at 14850' KIAS is 123 and climb rate is 866 fpm N1=97% N2= 100% and ITT=825


I turn off the autopilot and nose over into level flight then 10 degrees nose down but speed continues to decrease. At 118 knots the AC stalls. My reading of tech specs (not the IRIS manual) is Vs=105 knots. The Italian airforce tested paratroop and LAPES drops from a C-27J at 110 - 140 knots so a stall at 118 knots with the nose down and power on seems unusual.


I downloaded the installer on Dec 22, 2011 so I have whatever FDE / .cfg that was available at that time:

//IRIS Platinum Series C-27J Spartan for FSX


//1.2 Build (120)

[GeneralEngineData]
engine_type = 5
fuel_flow_scalar = 0.35
engine.0 = 10, -17, 0
engine.1 = 10, 17, 0
min_throttle_limit =-0.25


//*****************************************************************************


[TurbineEngineData]
fuel_flow_gain = 0.005
inlet_area = 1.0
rated_N2_rpm = 14267
static_thrust = 173.2
afterburner_available = 0
reverser_available = 1


//*****************************************************************************


[turboprop_engine]
power_scalar = 1.0
maximum_torque = 23876 //Based on SHP of 4637HP at 1020 Prop RPM
powerspecificfuelconsumption= 1


//*****************************************************************************


[propeller]
thrust_scalar = 1.2 //Propeller thrust scalar
propeller_type = 0 //0=Constant Speed, 1=Fixed Pitch
propeller_diameter = 13.5 //Propeller Diameter, (feet)
propeller_blades = 6 //Number of propeller blades
propeller_moi = 36.72 //Propeller moment of inertia
beta_max = 75 //Maximum blade pitch angle for constant speed prop, (degrees)
beta_min = 10 //Minimum blade pitch angle for constant speed prop, (degrees)
min_gov_rpm = 200 //Miminum governed RPM
prop_tc = 0.025 //Prop time-constant
gear_reduction_ratio = 13.98 //Propeller gear reduction ratio
fixed_pitch_beta = 0 //Fixed pitch angle of fixed pitch prop, (degrees)
low_speed_theory_limit = 80 //Speed at which low speed theory becomes blended in (feet/second)
prop_sync_available = 1 //Prop synchronization available? 0=FALSE, 1=TRUE
prop_deice_available = 1 //Prop de-icing available? 0=FALSE, 1=TRUE
prop_feathering_available = 0 //Prop feathering available? 0=FALSE, 1=TRUE


min_rpm_for_feather = 500 //Minimum RPM for prop feathering
beta_feather = 90 //Feathering pitch angle (degrees)
power_absorbed_cf = 0.95 //Coefficient of friction for power absorbed by propeller
prop_reverse_available = 1 //Prop reverse available? 0=FALSE, 1=TRUE
minimum_on_ground_beta = 1.0 //Miminum pitch angle on ground, (degrees)
minimum_reverse_beta = -4.0 //Minimum pitch angle in reverse, (degrees)


prop_auto_feathering_available = 0 //Prop auto-feathering available? 0=FALSE, 1=TRUE
defeathering_accumulators_available = 0 //Defeathering accumulators available? 0=FALSE, 1=TRUE

 

[warchild]

ok, a couple things i see right off that could help out a bit...

prop_feathering_available = 0 //Prop feathering available? 0=FALSE, 1=TRUEsho

should be

prop_feathering_available = 1 //Prop feathering available? 0=FALSE, 1=TRUE


minimum_reverse_beta = -4.0 //Minimum pitch angle in reverse, (degrees)

should be

minimum_reverse_beta = -11.0 //Minimum pitch angle in reverse, (degrees)


and


prop_auto_feathering_available = 0 //Prop auto-feathering available? 0=FALSE, 1=TRUE
defeathering_accumulators_available = 0 //Defeathering accumulators available? 0=FALSE, 1=TRUE

should be

prop_auto_feathering_available = 1 //Prop auto-feathering available? 0=FALSE, 1=TRUE
defeathering_accumulators_available = 1 //Defeathering accumulators available? 0=FALSE, 1=TRUE

here's where the problem comes in.. I only developed the 1.0beta version of the FDE. I do not have access to the 1.2 fde as i didnt buy the plane and I dont have download capabilities from Iris's ftp site any more.. Outside of what i've given above, i do not know how to proceed.. But will try and think of something..

regarding takeoff weight and roll distance.. I've heard of this with the 1.2 version before. I honestly dont know why its happening because it didnt happen in 1.0 Again though, let me see what i can do, because the plane really is an enjoyable plane..

Pam

 

[TacomaSailor]

More Test Data - can't get above 17000 feet nor 242 knots

Here is some test data from a flight I took today from Miramar 60F at ground level. All speeds are KIAS , climb is fpm, and N1/N2 are % Altitudes are absolute – not AGL

TO Flaps 2 N1 97% N2 100% rotate@105 KIAS climb at 1000 fpm
Takeoff roll was over ½ Miramar 24R which is 11990’ long
Attempt to climb 1000 fpm to 600’ then accelerate to 160 KIAS
HOT engine alarms at 500’

Reduce throttle to N1 95%
Climb dropped to 800fpm @ 150 KIAS
Climb at 800fpm to 5000’



Flying straight and level on Autopilot at 15000 at 230 N1=87 N2=102 ITT=787.
I set SPD target to be 250 – engines spool up to N1=93 N2=102 and ITT goes to 828 but max KIAS after 5 minutes is 240.

Flying straight and level on Autopilot at 15000 at 240 N1=93 N2=102 ITT=828.
I set SPD target to be 225, VS=800, ALT=20400 – engines stay at N1=93 N2=102 and ITT stays at 828
Actual KIAS drops to 216 at 800 fpm as engines spool up N1=97 N2=102

At 17000’ at +800fpm N1=97 N2=102 speed starts dropping rapidly (about –30 knots/minute). I turned off the AP and had to maintain 3 degrees nose down to hold a speed of 178 KIAS. At the time I turned off the AP the elevator was trimmed to MAX Nose Up!

I climbed back to 16600’ and set the AP at 211 KIAS which the AC held at N1=83 N2=102 ITT=759

I then set the AP ALT REF to 17500 and VS at 800 fpm. Engine spooled up to N1=92 M2=103 ITT=783.

The AC climbed to 17100 at which time the speed again began rapidly dropping. I set the ALT REF at 17000 but the speed continued to drop even as the AC leveled out. I again had to hold the nose at 3 degrees down and could not level out until 15500.

ANOTHER TEST SERIES:
Flying straight and level on Autopilot at 5000 at 225 N1=86 N2=102 ITT=815.
I set SPD target to be 225, VS=1000, ALTREF=20000 – engines spool up to N1=100 N2=92-94 and ITT stays at 822-835.

The climb stays at 222-224 KIAS and 980-1020 fpm to 16800’.

By the time the AC is at 17000’ the KIAS is 189 and the climb is 934fpm.
At 17500’ the KIAS is down to 135 and the climb is 830fpm N1=96 N2=106 ITT=806 (down 25 degrees ??) and fuel flow has almost doubled

I push the nose down to –5 degrees and finally level out at 16320 at a speed of 138KIAS. The throttles are at MAXCONT N1=96 N2=106 ITT=806 and I can not maintain level flight at 138. Holding the nose level causes speed to bleed off at 30 kts/min.

I repeat the procedure several more times and it is not until 13300’ that I can maintain 160 KIAS in level flight.

At that point I can again climb to 16500’ at 180 KIAS and do it all over again.

MAX CLIMB RATE
Testing shows the max climb rate (fpm) at which the AC can hold a speed of 190 - 200 KIAS is
15000-16800 800 fpm
16800-19200 700 fpm
19200-22100 600 fpm
Any attempt to climb above 22500 results in a stall no matter how low the rate of climb.

DOES that seem reasonable?


SUDDEN LOSS OF SPEED TAPE AT ALTITUDE
The following problem occurs in about 1/2 my flights above 15000'. All ice protection is turned on.

Flying straight and level on Autopilot at 15400 at 211 KIAS N1=87 N2=102 ITT=787 80 minutes into flight

IAS drops to 0 on Speed Tape but shows 270 on HUD Speed Target is 260. Engine spool up to max power – after 60 seconds Speed Tape suddenly jumps to 270 but by then engines are HOT and if the SPD target is left at 260 the engines eventually catch fire.

What is going on??

Can any of you FDE folks help with this?

 

[warchild]

I've been running some tests with modifying the 1.0 fde. irregardless of what i change, the plane goes whacko. those arent my numbers in there. I know i was given credit for the flight model, but that isnt my flight model, and the fact that if you change anything at all causes the plane to malfunction is totally disheartening to me.. I havent a clue what to do or where to start. I'll keep working on it though.. Till then, let me ssend you the 1.0 version. it at least flies..
Pam

 

[Sieggie]

I frequently, but not always, have a severe imbalance between the two engines. When I started the engines this time I found for left and right:

RPM 90% 52%
ITT 735 735
N1 63 63
N2 90 52
FF 20 49
PSI 83 77

PROP FEATHERING
The manuals says "OH-Y-1 - Left and Right Prop Control switchesManually sets the prop pitch between FEATHERED, UNFEATHERED and NORMAL, where NORMAL is controlled by the AUTOFEATHER system"

When I click on either feather control the red guard switch opens but if I touch, right click, left click or do anything else to the toggle that is exposed - the red guard just flips down and nothing else changes.

I've tried this with PROP SYNCH ON/OFF and AUTOFHR ON/OFF

HOW do I feather or unfeather the props?

Thanks for any suggestions

I had this problem until I realized each time you click the prop control switches it will change. If you look very carefully, you will see the switch just peak out the top of the guard when you left click the switch repeatedly. You must be in normal, Left clicks move from Normal (cant see Toggle sw) to UnFeathered (Cover Open) to Feathered (Cover Closed Switch Peaking out top). Right Click Selects the other way frim feathered through Normal. The switch must be in Normal (Cover Closed, toggle not visible) for the engine to perform correctly.

Dave

 

[Victory103]

Tacoma, I'm leaning towards Dave's above theory. I have just finally been able to download/install and fly the 27J under ISA conditions. Following the other FDE thread, I made the .cfg changes right away to my 1.2 install. After a complete cold/dark start and finally getting the autofeather switch to "unpeek", my test numbers are closer to normal climb rates/speeds although as discussed in the the other thread my MCP speeds seem off for a fully loaded aircraft. Looking at my aircraft.cfg, I have the same settings as you that Pam pointed out. My next test flight is going to be all single engine work at altitude, this should really give the autofeather a work out and determine the switch position in the overhead panel.

 

[warchild]

yeahhhh, i installed the 1.2 fde on top of the 1.0 visual model and gauges. The result was that the port engine immediately caught fire on start up. this has happened twice.. Apparently you can use the 1.0 fde with the 1.2 aircraft, but not the other way around.. I understand Davids need for copy protection, but to me, this is extreme, and painful..
Pam

 

[TacomaSailor]

Lots more details - Consistent HOT takeoff & stall at 18000'

I had previously verified the prop control was Normal (Red Guard closed) but just tried another series of tests with 100% certainty the prop control is Normal.

Here are three different anamalous flight charcteristics I have experienced in the last three days of flying the C-27J.

Would it be better to take this discussion to the IRIS forum?

ABYSMAL TAKEOFF PERFORMANCE / HOT ENGINES
NOTE: C-27J website specifies takeoff in 1900' with a 3 minute climb to 10000' (3333 fpm)

TO flaps 2 N1=100% N2=100%
3800' & 30 seconds from brake release to reach 105 kts
Rotate at 106
Airborne at 108 - climb at 1000 fpm
HOT engines at 150' AGL
Pull throttles back to 85% N1 99% N2
30 seconds later HOT alarm goes out
165 KIAS Climb 1000 FPM

TO flaps 2 N1=100% N2=87%
4900' & 34 seconds from brake release to reach 105 kts
Rotate at 106
Airborne at 108 - climb at 1000 fpm
170 KIAS Climb 1000 FPM (missed approach climb out performance)
HOT ENGINE ALARM at 2500’ AGL N1=100 N2=86 ITT=842

TO flaps 2 N1=100% N2=85%
6900' & 40 seconds from brake release to reach 120 kts (recommended TO speed)
Rotate at 108
Airborne at 120
170 KIAS Climb 1000 FPM (missed approach climb out performance)
Max climb rate achieved = 480fpm at 170 KIAS
Did not trigger a HOT engine alarm.


QUESTIONS:
1. Why is the takeoff performance so lacking? 4000’ takeoff roll for an unloaded tactical transport is not acceptable.
2. How do I takeoff without the engines overheating (N2=85% = HOT alarm in 40 seconds)
3. How do I make a “tactical takeoff” (C-27J literature says this can be done in less than 2000’) if the engines overheat on a 4200’ takeoff N2=84%?


CONSISTENT STALL AT 18000’ or NO CLIMB THRU 18000’

Flying straight and level on Autopilot at 5000 at 225 KIAS N1=86 N2=102 ITT=815.
I set SPD target to be 225 KIAS, VS=1000 fpm, ALTREF=20000 – engines spool up to N1=100 N2=92-94 and ITT stays at 822-835.

The climb stays at 220-224 KIAS and 980-1020 fpm to 14000’ at which time the KIAS has decayed to 216 but is holding steady there. N1=99 N2=94 ITT=835

At 16800’ KIAS is down to 208 climb=970 fpm N1=99 N2=94 ITT=816 and the airspeed is dropping at 40 kts/minute

I decrease the climb rate to 800 fpm but speed decays to 170 KIAS by 17100 and climb is down to 700 fpm

I decrease the climb rate to 700 fpm but speed decays to 144 KIAS by 17300 and climb is down to 600 fpm

I decrease the climb rate to 500 fpm but speed decays to 120 KIAS by 17400 and climb is down to 350 fpm – preSTALL wing buffeting occurs – wings started rocking!

I disconnect the AP and point the nose down at 3 degrees

At 16800’ I am back to 170 KIAS and reset the AP for a 700 fpm climb at 190 KIAS. The AC climbs at the specified rate and slowly accelerates to 190 KIAS in the next 45 seconds.

This time the AC climbs at 187 – 191 KIAS and 700 fpm to 22000’ N1=99 N2=102 ITT=732 (?? 95 degrees lower than at 15000’)

I then descended to 9000 and repeated the climb to 22000 at 225KIAS/700 fpm.

The speed and climb were stable 221-225KIAS and 690-720 fpm up to 18100 where airspeed starting dropping at 60 kts/minute and climb dropped to 675 fpm. N1=100 N2-94 ITT=773 the ITT went from 830 at 15000 to 773 at 17800???

At 18500 KIAS=157 climb=519 fpm ITT=765 ???

At 18600 I disconnected the AP and tried to hold level flight. KIAS=119 N1=99 N2=97 but speed continued to decay at a high rate. I pushed the nose over and regained 160 kts at 16800 after descending at 2500 fpm.

QUESTION:
If the AC can climb at 190KIAS/700 fpm from 16800 to 22000 why can’t it climb at the same rate from 10000 to 22000? It repeatedly stalled going from 15000 to 18000 at 190KIAS & 700fpm.


SPEED TAPE GOES TO 0 WHILE FLYING STRAIGHT AND LEVEL


All ice protection is ON

I leveled the AC at 160 KIAS 16700’ and engaged the AP/IAS/ALT. Immediately the speed tape went to 0 and AP SPD target went to 0. I reset the SPD target to 160 but could not get the speed tape off of 0. The AP spooled the engines to full emergency power, N1=104 N2=110, trying to regain the missing speed.

If I do nothing the engines burst into flames in a few seconds.

I manually flew the AC to 160 KIAS (Ground Speed=190) at 16700’ and trimmed to stay at that altitude and speed. I allowed the AC to fly for several minutes in that configuration with NO Autopilot. I then engaged the AP/IAS/ALT. Within 10 seconds the speed tape went to 0.

The FSX Shift+Z display also showed 0 KIAS, the GPS showed 110 kts ground speed and the VS dial showed –43 fpm.
(It is physically impossible to go from 160 KIAS/GS 190 to GS 110 in 10 seconds while staying at the same altitude!)

I disconnected the AP and IAS and found the plane was in a flat stall – I could raise and lower the nose but the VS quickly hit –5000 fpm.
QUESTION: How did I enter a flat stall when 10 seconds earlier I was stable at 160 knots and had been for several minutes?

I pushed the nose over to –15 degrees and quickly hit 200 knots GS on the GPS but the speed tape showed 0 KIAS and VS hit –8900 fpm. I slowly eased the nose up pulling 2 G. The VS went to +3400 fpm but the speed tape remained at 0.

I trimmed the elevators for level flight at 15100’ with throttles at N1=99 N2=84. Ground Speed went to 255, the flight stayed level but the speed tape never came off 0 nor did Shift+Z nor did the HUD display and speed.

I switched to the Dassault Falcon 50 jet and found a speed indication of 225 KIAS and 254 GS.

I switched back to the C-27J and the speed tape was working again but only showed 196 KIAS and 230 kts GS. Within 10 seconds the speed tape went back to 0! I reloaded a different version of the C-27J and the same thing happened – good speed tape reading for 10 seconds – then 0.

This problem occurs on almost every flight at some point. It has happened at 10,000' / 15,000' / 22,000'

QUESTION:
What causes the KIAS to go to 0 at altitudes greater than 15000’?

All ice protection is ON

CAN'T STAY AT 20400' STRAIGHT AND LEVEL
Had been flying AP/IAS/ALT/HDG at 20400/260KIAS for many minutes

Suddenly speed started decaying - I let it drop to 135 KIAS with a VS of -450 (N1=105 N2=97 ITT=745) to see if the AP could sort it out. At 18900' I returned to manual control and pointed the nose down 3 degrees. The plane accelerated to 141 KIAS -1200fpm but WOULD NOT accelerate beyond that speed.

I dropped the nose to -6 degrees VS=-3500 fpm and was able to accelerate to 150 kts in 10 seconds

What kind of flight dynamics are those? -3500 fpm and engines at full power and the AC will not accelerate?

I trimmed for level flight (attitude +2 degrees 15000') with N1=101 N2=95 at 151 knots and within seconds the VS was -1250 fpm.

I trimmed nose up 5 degrees (14500') to get a VS of -400 and speed decayed to 125 KIAS within 20 seconds

THE AIRPLANE IS NOT FLYABLE IT RANDOMLY FALLS OUT OF THE SKY!