Apparatus and method for computing wind-sensitive optimum altitude steps in a flight management system

• US 5,574,647 A
• Filed: 10/04/1993
• Issued: 11/12/1996
• Est. Priority Date: 10/04/1993
• Status: Expired due to Term

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: Liden, Sam P.
• Primary Examiner(s): Teska, Kevin J.
• Assistant Examiner(s): PHAN, THAI Q
• Application Number:
  US08/131,069
• Time in Patent Office: 1,135 Days
• Field of Search: 364/442, 364/444, 364/440, 364/433, 364/443, 364/420, 364/448, 73/178 R, 244/180-182, 244/183, 340/969, 340/970, 340/977, 340/978
• US Class Current: 701/8
• CPC Class Codes: G05D 1/0005 with arrangements to save energy
• CPC Class Codes: G05D 1/0615 to counteract a perturbation, e.g. gust of wind

Abstract

An apparatus and method for determining the best legal flight altitudes, and the best points at which to change to a new legal flight altitude, such that the cost of the flight is minimized, but subject to filtering to prevent excessive changes in altitude.

Claims

1. The method of predicting the most economical legal altitudes to fly an aircraft over a flight plan, the method consisting of a sequence of prediction intervals the end of the last one of which defines the current state of that prediction interval and for which maximum and minimum permitted altitudes exist, comprising the steps of:

A. Determining the maximum and minimum permitted altitudes at the end of the interval;

B. Determining the legal altitudes from the minimum to the maximum altitudes at the end of the interval;

C. Calculating the Specific Cost for each such determined legal altitude utilizing the equation;

SpCost=(if+k)/vg where

SpCost is cost/unit distance, ff is fuel flow as determined from a function of air speed, altitude, temperature and gross weight, k is the non-fuel cost per unit time divided by the fuel cost/unit weight and vg is ground speed as determined from a function of true air speed and wind direction and velocity;

D. Selecting a candidate legal altitude at which SpCost, calculated in step C is the lowest;

E. Comparing the candidate legal altitude from step D with the altitude of the current state; and

E1. If they are the same, continuing normal prediction without changing altitudes;

or

E2. If the candidate legal altitude is different than the altitude of the current prediction state, determining determine and saving a point in the prediction interval as the candidate step climb point the point being where specific costs at the prediction state altitude and the SpCost at the candidate legal altitude are equal;

F. Predicting the direct operating cost of the flight for each of the legal altitudes of step B by performing a trial prediction over a pre-determined distance interval for each such legal altitude; and

G. Comparing the direct operating cost for each such legal altitude from step F and identifying that one which gives the lowest direct operating cost.

2. The method of claim 1 further including the step:

H. Comparing the identified altitude with the current prediction state altitude and,

H1. if the same, inhibiting climbs and descents for a distance DN;

H2. if identified altitude is greater than the prediction state altitude, doing a step climb to that altitude and inhibiting further step climbs and descents for a distance DC; and

H3. if identified altitude is less than the prediction state altitude, doing a step descent to that altitude and inhibiting further step climbs and descents for a distance DD.

3. Apparatus for determining the lowest cost altitude profile at which to fly an aircraft, comprising:

a flight management computer having a first plurality of inputs including a flight plan, a cost index and weather forecast data;

a second plurality of inputs representing the state variables of the aircraft flight connected to the computer;

said computer receiving the inputs and predicting (simulating) flight along the flight plan and computing the cost per unit time for each legal altitude between a predetermined minimum and maximum altitude from the equation SpCost=(ff+k)/vg where ff is fuel flow and a function of air speed, altitude, temperature and gross weight, k is a constant cost index scaled to the units of ff and vg is ground speed and a function of true air speed and forecast wind direction and velocity, said computer selecting the altitude which has the least cost.

4. Apparatus according to claim 3 wherein the second set of inputs includes time input means, distance to destination input means, altitude input means, gross weight input means, true airspeed input means and flight path angle input means.

5. Apparatus according to claim 3 further including current wind and temperature input means connected to the computer.

6. Apparatus according to claim 4 further including current wind and temperature input means connected to the computer.

7. Apparatus according to claim 3 further including display means connected to the computer.