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Illustrated technical information covering Vol 2 Over 800 multi-choice systems questions Study notes and technical information Close up photos of internal and external components A compilation of links to major 737 news stories with a downloadable archive Illustrated history and description of all variants of 737 Detailed tech specs of every series of 737 Databases and reports of all the major 737 accidents & incidents General flightdeck views of each generation of 737's Description & news reports of Advanced Blended Winglets Press reports of orders and deliveries A collection of my favourite photographs that I have taken of or from the 737 Details about 737 production methods A compilation of links to other sites with useful 737 content Get the book of the website A quick concise overview of the pages on this site

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Contents

Fuel Consumption Formulae:

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*** Updated 16 Sep 2016 ***

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Speed, Height, Distance conversion

Level flight deceleration allow 10kts/nm & 1kt/sec (deceleration is faster at lower weights)

Descending deceleration allow 5kts/nm & 0.5kt/sec

Idle descent allow 3nm/1000'

 

Approach Profile Planning

Aim for 250kts, 10,000ft by 30nm out

Aim for 210kts, On ILS at 12nm

 

Cruise N1

N1 = (2 x Alt/1000) + 10   eg at FL350 = 70+10 = 80% N1

or

FF = (IAS*10)/2 -200  eg 250kts = 2500/2 -200 = 1050 kg/hr/engine

 

N1's & Pitch Attitudes

Phase of flight

%N1

Attitude (deg nose up)

Level Flight:

250kts

65

4

210kts

60

6

Flap 1, 190kts

60

6

Flap 5, 180kts

62

7

Gear down, flap 15, 150kts

70

8

Gear down, & on glideslope:

Flap 15, 150kts

52

4.5

Flap 25, 140kts

52

4

Flap 30, Vref + 5

55

2.5

Flap 40, Vref + 5

62

1

All the above based on a gross weight of 47.5, N1 may vary by 5% and attitude by 2 at other weights.

Add 2% N1 in turns.

For single engine add 15% N1 + 5% N1 in turns.

 

Climb Speeds

If ECON info not available, use 250KIAS until 10,000ft then 280KIAS/M0.74 thereafter.

Best Angle = V2 + 80

Best Rate = V2 + 120

 

Kinetic Heating

Increases TAT by approximately 1/10kts IAS

 

Driftdown

Driftdown speed and level off altitude are for the terrain critical case; if terrain is not critical you may accelerate to Long Range Cruise (LRC), this will cost approximately 3000ft. Otherwise slowly accelerate to LRC at the level off altitude as weight reduces with fuel burn. If anti ice is required, the altitude penalties are severe. See table below for figures (QRH PI.13.7).

 

 

Altitude penalty for engine bleed requirements

737-300

737-700

Bleed requirements

Terrain critical

LRC

Terrain critical

LRC

Eng Anti-ice ON

-1500ft

-4000ft

-5600ft

-5900ft

Eng & Wing Anti-ice ON

-4800ft

-7600ft

-12500ft

-13000ft

 


 

Fuel Consumption Formulae

 

Optimum FL   (FPPM p2.1.1)

 

Altitude away from optimum

Fuel Mileage Penalty %

737-300 M0.74

737-700 M0.78

2000ft above

1

2

Optimum

0

0

2000ft below

2

2

4000ft below

4

5

8000ft below

11

14

12000ft below

20

24

 

 

Step climb & wind/altitude trade    (FPPM p3.2.16)

 

Step climb under consideration

Break  even wind

737-300 M0.74

Break  even wind

737-700 M0.78

FL290 FL330

< 34Kts

< 75Kts

FL310 FL350

< 25Kts

< 69Kts

FL330 FL370

< 12Kts

< 55Kts

FL370 FL410

N/A

< 24Kts

 

The 737 burns approx 30kg/min. Hence subtract (30kg x reduced trip time in mins) from the trip fuel at the proposed level. If this figure is less than the trip fuel for the planned flight level, the lower level is justified.

 

Trip Fuel Reduction = Weight reduction x Flight time in hrs x 3.5%

Eg: 10 pax less over a 2hr flight = 1000kg x 2 x 3.5% = 70kg lower trip fuel.

 

Landing Flaps

Flap 30 uses 25kgs less fuel than flap 40 from 1500 ft to touchdown.

 

Anti Ice

Engine Anti-ice burns 90 kg per hour.

Engine + Wing Anti-ice burns 250 kg per hour.

 

Non-Normal Configurations

Compared to 2 Engine LRC at Optimum Altitude for any given weight:

Engine Out LRC burns 21% more fuel.

Engine Out LRC increases Time Interval by 13%.

Depressurised LRC (2 Engines@10,000') burns 49% more fuel.

Depressurised LRC increases Time Interval by 20%.

Gear Down burns 89% more fuel! Gear Down increases Time Interval by 29%.

Hint. you can check the Depressurised figures quoted above by entering 10,000' as a "step altitude" in the CRZ page and compare the fuel remaining at your destination.

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