US4922258A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for determining aircraft flight altitude
Assignee: Northrop Grumman Litef GmbH
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Filing: 1987-11-12
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Granted: 1990-05-01
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Expires: 2007-11-12
Abstract
Abstract A method for determining the flight altitude h above ground of an aircraft equipped with a radar altimeter and an additional (baro-inertial) altitude measuring device or a course and position reference system capable of determining altitude. The method relies upon restriction of high-frequency emissions from the radar altimeter to very short periods of time. The radar altimeter measures h RO within the high-frequency intermission intervals to calibrate the altitude value supplied by the other altitude-measuring device. The method permits the omission of any radar altimeter from aircraft-launched missiles without degrading system performance.
Inventors
- 👤 Wolfgang Hassenpflug
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 20:33
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/86; G01C; G01C5/00; G01C5/005
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
169 words
A method for determining the altitude above ground (h) of an aircraft that is equipped with a radar altimeter and a flight-altitude measuring device comprising the steps of: (a) intermittently repeating the high-frequency signal for obtaining radar altitude (h RO ); (b) the intermission intervals between repetitions of said high-frequency signal being substantially longer than the transmission time required to obtain a valid radar altimeter measurement whereby said high-frequency repeated signals are relatively brief and the time interval between successive repetitions of said high-frequency signal is controlled to be a random variable having a given statistical distribution between predetermined minimum and maximum durations; then (c) subtracting the current value of radar altitude h RO from the altitude value (h B ) that is supplied by said flight-altitude measuring device; and (d) storing the difference (δh) for at least the duration of the following transmission interval; and then (e) providing the current valid altitude h as an altitude value h B corrected by the amount of said stored difference δh.
Claim 2
Independent Claim
169 words
A method for determining the altitude above ground (h) of an aircraft that is equipped with a radar altimeter and a flight-altitude measuring device comprising the steps of: (a) intermittently repeating the high-frequency signal for obtaining radar altitude (h RO ); (b) the intermission intervals between repetitions of said high-frequency signal being substantially longer than the transmission time required to obtain a valid radar altimeter measurement whereby said high-frequency repeated signals are relatively brief and the time interval between successive repetitions of said high-frequency signal is controlled to be a random variable having a given statistical distribution between predetermined minimum and maximum durations; then (c) subtracting the current value of radar altitude h RO from the altitude value (h B ) that is supplied by said flight-altitude measuring device; and (d) storing the difference (δh) for at least the duration of the following transmission interval; and then (e) providing the current valid altitude h as an altitude value h B corrected by the amount of said stored difference δh.
Claim 3
Independent Claim
165 words
A method for determining the altitude above ground (h) of an aircraft that is equipped with a radar altimeter and a flight-altitude measuring device comprising the steps of: (a) intermittently repeating the high-frequency signal for obtaining radar altitude (h RO ); (b) the intermission intervals between repetitions of said high-frequency signal being substantially longer than the transmission time required to obtain a valid radar altimeter measurement whereby high-frequency repeated signals are relatively brief and the rate of repetition of said high-frequency signal is adjusted to correspond approximately to the rate of variation in height of the overflown terrain; then (c) subtracting the current value of radar altitude h RO from the altitude value (h B ) that is supplied by said flight altitude measuring device; and (d) storing the difference (δh) for at least the duration of the following transmission interval; and then (e) providing the current valid altitude h as an altitude value h B corrected by the amount of said stored difference δh.
Claim 4
Independent Claim
165 words
A method for determining the altitude above ground (h) of an aircraft that is equipped with a radar altimeter and a flight-altitude measuring device comprising the steps of: (a) intermittently repeating the high-frequency signal for obtaining radar altitude (h RO ); (b) the intermission intervals between repetitions of said high-frequency signal being substantially longer than the transmission time required to obtain a valid radar altimeter measurement whereby high-frequency repeated signals are relatively brief and the rate of repetition of said high-frequency signal is adjusted to correspond approximately to the rate of variation in height of the overflown terrain; then (c) subtracting the current value of radar altitude h RO from the altitude value (h B ) that is supplied by said flight altitude measuring device; and (d) storing the difference (δh) for at least the duration of the following transmission interval; and then (e) providing the current valid altitude h as an altitude value h B corrected by the amount of said stored difference δh.
References Cited (Backward Citations)
US4144571A
Cited
US4431994A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-04-30 | 1993-10-30 | 1994-05-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-04-30 | 1997-10-30 | 1998-05-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-04-30 | 2001-10-30 | 2002-05-01 | $7700.00 | Window Closed / Lapsed |