*How to calculate the Estimated Time Enroute (ETE Flight Time) for a Flight Segment.*

* 1st Step*: Determine the segment distance (Dist) for the flight using aeronautical

charts or tables giving distances between airports.

* 2nd Step*: Determine your segment cruise groundspeed (GS) – use your E6B air navigation computer and the forecast temperature and wind at your cruise pressure altitude, or use your personal knowledge of the aircraft true airspeed and your accurate estimate of the headwind or tailwind component at your planned altitude.

* 3rd Step*: Look up the

*climb/descent data (TTC, TTD, DTC, DTD)*with reference to your planned cruising altitude – use your

*Aircraft Flight Manual (AFM) Performance Section*.

* 4th Step*: Calculate the segment Estimated Time Enroute (

**ETE flight time**). The general formula for determining the estimated time enroute is –

ETE(1) = (60 * (Dist – DTC – DTD) / GS) + (TTC + TTD + TAD + AAL + HLD)

*(Note: The ’60’ factor seen in the equations on this page are there to convert hours to minutes.)*

where,

Dist = Segment Distance (GCNM; i.e., 312.)

ETE = Estimated Time Enroute (Minutes ; i.e., 77.6)

TTC = Time-to-Climb (Minutes; i.e., 23)

TTD = Time-to-Descend (Minutes; i.e.,18.4)

TAD = Takeoff and Departure (Minutes; i.e., 4)

AAL = Approach and Landing (Minutes; i.e., 5)

HLD = Estimated In-flight Delays (Minutes; i.e., 2)

DTC = Distance-to Climb (Nautical Miles; i.e., 84)

DTD = Distance-to Descend (Nautical Miles; i.e., 99.8)

GS = Cruise Groundspeed (Knots; i.e., 305)

*(Note: The above numbers are based on a flight from SAC to LAX in a CE-500 at FL370.)*

Then,

ETE(1) = (60 * (312 – 84 – 99.8) / 305) + (23 + 18.4 + 4 + 5 + 2) = (60 * (128.2 / 305)) + 52.4 = 25.2 + 52.4 = 77.6 Minutes.

*However, if we really work at it, we can change the general formula, ETE(1), to the equivalent –*

ETE(2) = 60 * (Dist / GS ) + (TTC + TTD + TAD + AAL + HLD) – (60 * (DTC + DTD) / GS)

*and, since the 2nd part of the formula (in blue type) is independent of the segment distance, we can separate it out as a constant –*

K_{Mins}= (TTC + TTD + TAD + AAL + HLD) – (60 * (DTC + DTD) / GS)

= ( 23 + 18.4 + 4 + 5 + 2) – (60 * (84 + 99.8) / 305) = 52.4 – 36.2 = 16.2 Minutes

*[Note: In this example, this is the amount your ETE will be off if you estimate your ETE flight time by simply dividing your segment distance by your cruise groundspeed!]*

*Then, we can simply divide the segment distance by the groundspeed, and add K _{Mins }to get the exact ETE Flight Time –*

ETE(2 )= (60 * (Dist/GS ) ) + K_{Mins }= 61.4 + 16.2 = 77.6 Minutes.

*If you’d rather work with distances, we can change the general formula, ETE(1), to the equivalent –*

ETE(3)= 60 * (Dist + ((TTC + TTD + TAD + AAL + HLD) * GS / 60) – (DTC + DTD)) / GS

*Since the part of the formula in blue type is independent of the segment distance, we can separate it out as a constant –*

*K _{Dist}* = ((TTC + TTD + TAD + AAL + HLD) * GS / 60) – (DTC + DTD)

*K _{Dist }= (23 + 18.4 + 4 + 5 + 2) * (305 / 60) – (84 + 99.8)* = 266.4 – 183.8 = 82.6 NM.

*Then, we can simply add K _{Dist }to the segment distance and divide by the groundspeed to get the exact ETE flight time –*

ETE(3) = (Dist + K_{Dist }) / (GS/60) = (312 +82.6) / (305/60) = 77.6 Minutes = 1.29 Hours.

Note: The above constants, K_{Mins} and K_{Dist} *, *are valid only when the actual flight is flown at the *cruise altitude* and with the *cruise groundspeed, TAD, AAL and HLD * used for their calculation.

*Use calculated ETE Flight Time to determine trip cost –*

Step 3: Determine the cost of the trip after rounding the flight time to the nearest tenth –

Cost = ETE * Cost per hour = 1.3 Hours * $1,575 = $2,048.

*Click Here for information on how to*

* calculate the fuel usage for a flight segment*.

FlightComp Systems does not recommend or advise that any operator use this information as a sole resource for any preflight planning activity.

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