TH-73A Limits

Question 1

Introduction Blurb

Answer 1

Compliance with the operating limitations in section 1 of this manual is mandatory. The helicopter must also be operated in accordance with the appropriate operating rules.

If aircraft structural, rotor or engine limitations are exceeded, record the fact on a maintenance action form, including limits exceeded, range, time beyond limits, and any additional data that would aid maintenance.

Question 2

Gas Generator Speed (N1)

Answer 2

Minimum 51%
Cautionary (autorotation only) 51 to 60%
Continuous operation 60 to 100.1%
Take-off (5 minutes) 100.1 to 103.2%
Maximum take-off (5 minutes) 103.2%
Transient (30 seconds) 103.8%

N:
-Transient must not be used intentionally
-IDLE N1 may decrease below 60% when the generator and other aircraft systems are turned on. This is normal.

Question 3

Power Turbine Speed (N2)

Answer 3

Minimum 95%
Cautionary 95 to 101%
Continuous operation 101 to 103%
Maximum 103%
Transient (10 seconds) 108%

C:
-As N2 indication of 103% corresponds with an actual value of N2 of 102.50% to 103.49%. The N2 transient range begins at 103.01%. Protracted operation at N2 values of 103% should be avoided to minimize the possibility of N2 overspeed.

N:
-Transient must not be used intentionally.

Question 4

Inter-Turbine Temperature (ITT)

Answer 4

Normal Operation

Maximum continuous 755 deg C
Take-off (5 minutes) 755 to 810 deg C
Maximum take-off (5 minutes) 810 deg C
Transient (5 seconds) 860 deg C

Starting

Maximum 870 deg C
Transient (2 seconds between 980-1090 deg) 1090 deg C

N:
-A linear variation applies above 870 deg C, ten seconds, and 980 deg C, two seconds
-Transient must not be used intentionally

Question 5

Engine Torque (TRQ)

Answer 5

Maximum continuous 100%
Take-off (5 minutes) 100-108.5%
Maximum take-off (5 minutes) 108.5%
Transient (6 seconds) 115%

N:
-Transient must not be used intentionally

Question 6

Rotor Limitations (NR) Power-On

Answer 6

Minimum 95%
Cautionary 95-101%
Continuous operation 101-103%
Maximum 103%
Transient (10 seconds) 108%

N:
-Transient must not be used intentionally.

Question 7

Rotor Limitations (NR) Power-Off

Answer 7

Transient (10 seconds) 80%
Minimum 90%
Continuous operation 90-110%
Maximum 110%

Question 8

Fuel Pressure Limitations

Answer 8

Cautionary 0-7 psi
Continuous operation 7-25 psi
Maximum 25 psi

Question 9

Minimum Fuel Limitations

Answer 9

Minimum fuel on landing shall be no less than 50 lb in the No. 1 cell.

W:
-Sideward flight and crosswind hovering when indicated fuel quantity is less than 22 lb may result in engine flameout.

N:
-The No.1 and No.2 fuel cells each contain 9 lb of unusable fuel.

Question 10

Engine Oil Pressure Limitations

Answer 10

Minimum 40 psi
Cautionary (with N1 <72%) 40-80 psi
Continuous operation 80-110 psi
Maximum 110 psi

N:
-During cold starting conditions the oil pressure can temporarily exceed 110 psi; it reduces as oil temperature increases.

Question 11

Engine Oil Temperature Limitations

Answer 11

Minimum OAT for starting -25 deg C
Continuous operation 10-115 deg C
Maximum 115 deg C
Transient (5 minutes with N1 at 61 +/-1% 127 deg C

Question 12

Main Transmission Oil Pressure

Answer 12

Minimum 30 psi
Continuous operation 30-55 psi
Cautionary 55-70 psi
Maximum 70 psi

Question 13

Main Transmission Oil Temperature

Answer 13

Minimum OAT for starting -25 deg C
Continuous operation 0-115 deg C
Maximum 115 deg C

Question 14

Engine Starter Limitations

Answer 14

The engine starter duty cycle is the following:

On battery:
1. 40 seconds on, 60 seconds off.
2. 40 seconds on, 60 seconds off.
3. 40 seconds on, 30 minutes off.

With external power:
1. 25 seconds on, 30 seconds off.
2. 25 seconds on, 30 seconds off.
3. 25 seconds on, 30 minutes off.

Question 15

Generator Load Limitations

Answer 15

Continuous operation 0-200 A
Maximum 200 A
Transient (5 seconds) 300 A

Question 16

Auxiliary Generator Load Limitations

Answer 16

Continuous operation 0-150 A
Maximum 150 A
Transient (5 seconds) 150 A

Question 17

Hydraulic Fluid Pressure Limitations

Answer 17

Minimum 1200 psi
Cautionary 1200-1400 psi
Continuous operation 1400-1600 psi
Maximum 1600 psi

Question 18

Vne (Power-ON/OFF)

Answer 18

See Figure 4.12-3

Question 19

Vne (Max. IFR airspeed)

Answer 19

Lesser of 145 KIAS or Vne (Power On)

Question 20

Vmini (Min. IFR airspeed)

Answer 20

60 KIAS

Question 21

Vmin APP (Min. IFR Approach airspeed)

Answer 21

60 KIAS

Question 22

Vmax APP (Max. IFR Approach airspeed)

Answer 22

130 KIAS

Question 23

Minimum airspeed in autorotation (without close external references)

Answer 23

60 KIAS

Question 24

Maximum airspeed with torque between 100 and 108.5% (take-off power range)

Answer 24

75 KIAS

Question 25

Vne with one or both doors open or removed

Answer 25

85 KIAS

Question 26

Vne during doors opening and closing operation

Answer 26

70 KIAS

Question 27

Maximum speed for searchlight extension, orientation and retraction

Answer 27

120 KIAS

Question 28

Vne with searchlight extended

Answer 28

No change with respect to the basic NFM

Question 29

Vne with external loads attached to cargo hook

Answer 29

From sea level to 5000 ft 100 KIAS Above 5000 ft Decrease 3 kt every 1000 ft Controllability and stability of the load may limit the airspeed of the rotorcraft with an external load. Particular rotor-craft load combination flight characteristics may reduce the limits above. N: -Caution should be exercised, when carrying external cargo, as the handling characteristics and controllability may be affected by the size, weight, and shape of the cargo load, as well as by the length of the sling.

Question 30

Maximum forward speed at touchdown after engine failure

Answer 30

50 KGS

Question 31

External Hoist Maximum Operating Limit Speed (Vne)

Answer 31

Hoist operation (cable reeling-in/out, load raising or lowering) is permitted with aircraft in stationary hover only. Aircraft horizontal translation with external hoisted load outside the aircraft cabin is approved up to 8000 ft density altitude (Hd) in accordance with the wind/ground speed azimuth envelope. The VS shall be limited to +/-200 ft/min. At altitudes higher than 8,000 ft, flight with external load outside the aircraft cabin is prohibited. Flight with external hoisted load shall be limited to reach a place suitable for load recovering. Hoisting or lowering an empty litter in open position is prohibited.

Question 32

Maximum operating altitude

Answer 32

15000 ft (4572 m) Hp

Question 33

Minimum ambient air temperature

Answer 33

-13 deg F (-25 deg C)

Question 34

Maximum sea level ambient air temperature

Answer 34

122 def F (50 deg C)

Question 35

Tell me about adiabatic lapse rate.

Answer 35

The maximum ambient air temperature for operation decreases with pressure altitude at the standard lapse rate of 2 deg C (3.6 F) every 1000 ft (305 m) up to 15,000 ft (4572 m)

Question 36

Nose-up operations

Answer 36

12 deg

Question 37

Side-up operations

Answer 37

10 deg

Question 38

Nose-down operations

Answer 38

2 deg

Question 39

Nose-down operations (unobstructed tail)

Answer 39

5 deg

Question 40

Maximum Gross Weight for ground operations (towing and Take-off prohibited)

Answer 40

6393 lb (2900 kg)