Patent US3754440A successfully refreshed from Google Patents.
US3754440A
Expired / Lapsed
US
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Helicopter lift margin determining system
Assignee: United States Department of the Navy
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Filing: 1972-08-16
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Granted: 1973-08-28
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Expires: 1992-08-16
Abstract
Abstract A system for determining in flight and continuously indicating to a helicopter pilot the lift margin of his craft is provided. Life margin as applied herein is the difference between the maximum available lift and the effective gross weight, both expressed in pounds, and is obtained from the ratio of lift to horsepower and the variation of the relative performance of the engine under ambient conditions. Input parameters of topping torque, hover torque, outside air temperature, static pressure, fuel weight, and rotor speed are both theoretically and empirically derived and combined to obtain maximum available lift and effective gross weight.
Inventors
- 👤 B Edgerton
- 👤 S Williams
- 👤 V Westcott
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 23:11
CPC Classifications
G; G01; G01C; G01C23/00
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
225 words
A method of determining continuously in flight by onboard computer the lift margin or additional weight that a helicopter may hover with based upon entering certain parameters into the computer which are measured at the time the helicopter is caused to perform certain maneuvers comprising: ascertainIng and recording the maximum available torque said engine can provide under standard conditions of 29.921 in g Hg pressure and a temperature of 150*C by topping maneuver; ascertaining and recording the effective gross weight of the helicopter by a hover or low speed cruise maneuver; ascertaining and recording the force necessary to lift the helicopter under varying conditions of rpm, altitude and temperature; ascertaining and recording the maximum available lift of the helicopter by using a theoretical and empirical expression for determining maximum available lift under varying conditions of rpm, altitude and temperature using maximum standard torque; applying said expression to values of said maximum available torque to determine maximum available lift at selected altitudes and temperatures; applying said expression to values of lifting force to determine the effective gross weight at said selected altitudes and temperatures; deriving the lift margin at said selected altitudes and temperatures by determining the difference between said values of maximum available lift and effective gross weight; and continuously displaying said values of maximum available lift and effective gross weight to the helicopter pilot.
Claim 2
Independent Claim
225 words
A method of determining continuously in flight by onboard computer the lift margin or additional weight that a helicopter may hover with based upon entering certain parameters into the computer which are measured at the time the helicopter is caused to perform certain maneuvers comprising: ascertainIng and recording the maximum available torque said engine can provide under standard conditions of 29.921 in g Hg pressure and a temperature of 150*C by topping maneuver; ascertaining and recording the effective gross weight of the helicopter by a hover or low speed cruise maneuver; ascertaining and recording the force necessary to lift the helicopter under varying conditions of rpm, altitude and temperature; ascertaining and recording the maximum available lift of the helicopter by using a theoretical and empirical expression for determining maximum available lift under varying conditions of rpm, altitude and temperature using maximum standard torque; applying said expression to values of said maximum available torque to determine maximum available lift at selected altitudes and temperatures; applying said expression to values of lifting force to determine the effective gross weight at said selected altitudes and temperatures; deriving the lift margin at said selected altitudes and temperatures by determining the difference between said values of maximum available lift and effective gross weight; and continuously displaying said values of maximum available lift and effective gross weight to the helicopter pilot.
Claim 3
Dependent Claim
40 words
The method as defined in claim 1 wherein the steps of applying said expression are performed by the same computer circuitry, whereby errors introduced by said same computer circuitry are canceled out in the determination of said difference of values.
Claim 4
Dependent Claim
102 words
The method as defined in claim 2 wherein the effective gross weight (EGW) of the helicopter is computed by a second expression as follows: EGW K6K7NOw + K8(P/Po)(K3 + K4T) 1 where Qw torque at weighing in psi, K3 0.9469, K4 0.003472, K6 0.00352, N engine rpm, P pressure in inches of Hg, Po standard pressure of 29.921 in. Hg, T temperature in *C, and K7 and K8 are 6.493 and 2225 respectively for changes in weight/changes in pressure ratios of from about 40 to about 58, and 7.639 and 1325 respectively for said ratios of from about 62 to about 100.
Claim 5
Dependent Claim
105 words
The method as defined in claim 3 wherein maximum standard torque is determined by a topping maneuver wherein the normal maximum allowable air speed at substantially the gross helicopter weight is noted at a desired test altitude after which the helicopter is accelerated to said air speed in level flight and then climbed at no greater speed until a 3 percent loss of rpm due to load on the engine is ascertained at which point the parameters of engine torque, outside air temperature and altitude are recorded; and means in said computer for converting said recorded parameters of temperature and pressure to said standard conditions.
Claim 6
Dependent Claim
73 words
The method as defined in claim 4 wherein EGW is determined by a cruise maneuver at 30 knots with data therein obtained modified to hover at zero airspeed by a third expression as follows: (EGW)H 1/(1-b) (EGW)30 + ((EGW)30/AGW)(LTO/(1-b)) -K1 (HP)pa ) where b 0.08725, LTO 1,904, AGW is the actual gross weight at any time and K1 (HP) par is negligible at 30 knots so that (EGW)H 1.0956 (EGW) 30 + 1431.1
Claim 7
Dependent Claim
209 words
A helicopter lift margin indicator for a helicopter having an onboard computer comprising: means for generating a standard voltage E proportional to the hydraulic pressure indicated by torquemeter gage at the time of topping of a helicopter whose lift margins are to be obtAined and modified to standard ambient conditions; means for generating a voltage T proportional to the outside air temperature at the time of said topping and the effect of said temperature on engine torque; means for generating a voltage proportional to the altitude of the helicopter at the time of said topping; means for generating a voltage proportional to the barometric pressure corresponding to the altitude at which the lift margin is to be determined; means for converting said altitude and barometric pressure voltages into a voltage Ps representing the effective static pressure for the conditions of altitude and barometric pressure; means for generating a reference voltage E* by modifying E proportionally according to the parameters T and Ps which reference voltage represents the maximum standard torque under the stated conditions; and means for digitally displaying said maximum standard torque; whereby the helicopter operator may note the appropriate value of maximum standard torque and enter said value into said computer to assist in determining additional parameters.
Claim 8
Dependent Claim
209 words
A helicopter lift margin indicator for a helicopter having an onboard computer comprising: means for generating a standard voltage E proportional to the hydraulic pressure indicated by torquemeter gage at the time of topping of a helicopter whose lift margins are to be obtAined and modified to standard ambient conditions; means for generating a voltage T proportional to the outside air temperature at the time of said topping and the effect of said temperature on engine torque; means for generating a voltage proportional to the altitude of the helicopter at the time of said topping; means for generating a voltage proportional to the barometric pressure corresponding to the altitude at which the lift margin is to be determined; means for converting said altitude and barometric pressure voltages into a voltage Ps representing the effective static pressure for the conditions of altitude and barometric pressure; means for generating a reference voltage E* by modifying E proportionally according to the parameters T and Ps which reference voltage represents the maximum standard torque under the stated conditions; and means for digitally displaying said maximum standard torque; whereby the helicopter operator may note the appropriate value of maximum standard torque and enter said value into said computer to assist in determining additional parameters.
Claim 9
Dependent Claim
120 words
The system as defined in claim 6 and further including means for combining T and Ps into a voltage sigma representing normalized air density; means for limiting E to representative values at which engine torque may be transmitted mechanically with safety; means for converting said limited E voltage representing psi to a voltage proportional to lift in lbs at said normalized air density; means for correcting said lift for ground effect; means for generating a voltage WFU proportional to the weight of fuel on board; means for summing lift in lbs and fuel weight WFU to determine the effective dry weight WN of the helicopter under the stated conditions; and means for digitally displaying said effective dry weight in lbs.
Claim 10
Dependent Claim
148 words
The system as defined in claim 7 and further including means for converting said values of T, Ps and maximum standard torque to a voltage proportional to available rotor horsepower expressed in psi, said available rotor horsepower converted to lbs at the stated conditions in said means for converting; said rotor horsepower in lbs corrected for ground effect in said means for correcting; means for summing WN, WFU and payload change in lbs to determine the effective gross weight EGW of the helicopter under the stated conditions; means for combining EGW and E to determine lift margin LM in lbs under said stated conditions; and means for displaying said values of EGW and LM continuously to the pilot, whereby the pilot may know immediately the additional load the helicopter may assume and may obtain the LM and EGW at other locations by inserting appropriate parameters into the computer.
References Cited (Backward Citations)
US3616691A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-08-27 | 1977-02-26 | 1977-08-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-08-27 | 1981-02-26 | 1981-08-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-08-27 | 1985-02-26 | 1985-08-28 | $7700.00 | Window Closed / Lapsed |