Limits Flashcards
Nf RPM
POWER ON: Minimum Nf is 97 percent. Maximum continuous Nf is 100 percent. Nf overspeeds are determined on a sliding scale depending on TOT, Nf percentage, and duration.
AVOID RANGE (STEADY STATE OPERATION): A 71 to 88 percent Nf steady state speed avoidance range is required for all operational practices. Flight in this range in excess of allowable transient limits requires turbine replace and shall be avoided. Any instance of such operation shall be recorded on a MAF to ensure documentation and shall include duration.
Notes:
1) Transient operation is defined as not remaining at a Nf speed of more than one second duration.
2) Consideration must be taken when practicing fixed pitch in a hover and low RPM recovery procedures.
3) Transient operation only is permitted in the speed avoidance range. Any exposure in the speed avoidance range must be minimized as much as possible. This limit applies to all flight and ground maintenance operational practices (including track and balance), except as noted below.
- During pretakeoff checks when rotating the twist frip to 70% Ng or full open is unrestricted, however, Nf should not purposely stabilize in the avoidance range.
- In an autorotation, with Nf split from Nf and throttle in the IDLE position, unrestricted operation within the speed avoidance range is permitted. Transient operation the speed avoidance range during recovery from autorotation is permitted.
Ng RPM
Idle gas producer (Ng) rpm is 62 +- 2 percent. The normal operating range is from 60 to 105 percent. A maximum transient of 106 % is allowed for 15 seconds.
Engine Oil Pressure
Minimum engine oil pressure is 50 psi with Ng below 79 percent. Minimum engine oil pressure with Ng between 79 and 94 percent is 90 psi. With Ng above 94 percent, the minimum engine oil pressure is 115 psi. Maximum engine oil pressure is 130 psi, except for temporary conditions up to 150 psi maximum immediately following a cold-weather start.
Engine Oil Temperature
Engine oil temperature limits are 0-107 degrees C
Rotor Engagement/Disengagement Wind Limitations
Up to 40 kts front 45, up to 25 knots both side 45s, up to 17 knots from back 45
Turbine Outlet Temperature
During Start
Up to 810 degrees - No limit
810-927 degrees - 10 seconds maximum
927 degrees - Maximum
During Power Transient
Up to 738 degrees - No limit
738-810 degrees - 5 minutes
810-843 degrees - 6 seconds
843 degrees - Maximum
Fuel
To avoid fuel freezing, do not allow indicated OAT in flight to dwell at or below the freeze point of fuel type in use. Increase airspeed and/or decrease altitude to maintain indicated OAT above the specific fuel freeze point. Minimum fuel reserve requirement for the TH-57B/C is 10 gallons.
Caution: Airframe and engine fuel filters may become blocked if fuel is chilled below its specific freeze point.
Rotor Limitations
POWER ON: Minimum Nr is 97 %. Maximum continuous Nr is 100 %
POWER OFF: The normal operating range is 90-107 %
Caution: Continuous operation in the 50-60 % Nr range may cause isolation mount damage.
Transmission Oil System Limits
Transmission oil pressure limits are 30-50 psi for continuous operation. Minimum oil pressure is 30 psi and maximum is 70 psi. Pressure indications between 50-70 psi shall be documented on a MAF upon completion of flight. Oil temperature limits are 15-110 degrees C. Check the transmission oil pressure with the twist grip full open.
Note:
1) Illumination of the TRANS OIL PRESS caution light is common while the twist grip is at flight idle, however, the gauge should indicate positive transmission oil pressure.
2) There is no detrimental effect to the transmission system with oil pressure between 50-70 psi with the transmission temperature within limits.
Torque
Maximum continuous torque is 85 %. Military power limit is 100 % for 5 minutes. Transient torque of 100-110 % is allowed for 5 seconds.
Fuel Pressure (Indicated)
Allowable fuel boost pump pressure is 4-30 psi.
Standby Generator Limitations (C)
Note: With main generator on, the standby generator loadmeter should indicate 10 % load or less. Momentary testing of standby generator under full bus load is permitted on the ground or in the air.
Prolonged operation of the standby generator while it is the primary power supply to the essential No. 1 bus is prohibited at speeds below 65 KIAS.
Rotor Brake Limitations
Rotor brake should be applied between 38-30 % Nr during normal operations.
Caution: Application of rotor brake below 30% Nr may cause damage to the drivetrain.
Starter Limitations
Limit Starter energizing time to the following:
Note: If a light off occurs within the first 20 seconds of the start sequence, the starter may be operated for 60 seconds with a 60 second cooling period. Three such attempts can be made in a 30 minute period, then wait 30 minutes to allow the starter to cool.
External Power:
25 seconds On
30 seconds Off
25 seconds On
30 seconds Off
25 seconds On
30 minutes Off
Battery:
40 seconds On
60 seconds Off
40 seconds On
60 seconds Off
40 seconds On
30 minutes Off
Airspeed Limits
Note: All airspeed values are calibrated airspeed except when indicated airspeed is specifically stated.
- Vne FCS OFF - 130 KIAS, FCS ON - 122 KIAS
(refer to figure 4-4 or 29-3 for Vne reductions based on GW and DA) - Sideward/Rearward flight
DA/Max sideward knots/Max rearward knots
0-1000/25/15
1-2/20/15
2-4/15/15
4-6/10/10
6-10/5/5
- Maximum rate of climb - 50 KIAS
- Minimum IFR speed (Vmini) - 65 KIAS
- Maximum airspeed with any combination of doors off - 110 KIAS
- Maximum autorotational airspeed is 100 KIAS
- Turbulence penetration airspeed is 80 KIAS
Altitude Limitations
Maximum operating altitude:
FCS OFF: 3000 pound gross weight and below - 20,000 ft PA; 18,000 ft DA
Above 3000 pound gross weight - 16,000 ft PA; 13,000 ft DA
IFR or FCS ON: 3000 pound gross weight and below - 11,500 ft PA; 13,500 ft DA
Above 3000 pound gross weight - 8,500 ft PA; 11,000 ft DA