CDOs – the flightdeck perspectiveCaptain Spencer Norton

AOA Environment Conference 28th April 2014

Why not all the time?• CDOs/CDAs are beneficial in terms of noise and fuel

efficiency

• Pilot needs to consider 3 things:

1. Height vs track miles

2. Speed reduction vs track miles

3. Rate of Descent vs track miles

Using our 3 times tableHeight vs track miles

8000ft x 3 = 24nm

7000ft x 3 = 21nm

6000ft x 3 = 18nm

5000ft x 3 = 15nm

4000ft x 3 = 12nm

Reducing our speedWe need to reduce our speed – we need distance to do this

1nm per 10 knots reduction of speed

For example:

To reduce from 250kts to 220kts

Δ 30kts

1x3 = 3nm required

Rate of Descent

Dependent on speed

A very ‘general’ rule of thumb:

1. Indicated speed – add a zero (220kts = 2200)

2. Divide this number by 2 (2200/2 = 1100fpm)

Example 2:

IAS = 160kts

1600/2 = 800fpm

Let’s put you in the hot-seat

Indicated Airspeed Altitude Groundspeed

Wind

Runway (EGPH 24)

Aircraft

Flight Management Computer

The ‘To’ Waypoint

Miles to go

You are inbound to EDI RWY 24, expecting no delay and have just taken up a radar heading from TARTN.

ATC have given you no indication of expected track miles to run. The CI24 point is at 10nm on the ILS for 24.

Speed = 250kts Altitude = 9000ft Miles to go = 30nm

Are we?

HIGH

ON PROFILE

LOW

PLAY YOUR CARDS RIGHT

Are we?

HIGH

ON PROFILE

LOW

PLAY YOUR CARDS RIGHT

This also agrees with the ‘raw data’ calculation of track miles required.

Height AAL 9000’ x 3 = 27

Decel to 220kts (1nm/10kts) 3 x 1 = 3 30 nm

This is actually one of the ‘gates’ we aim for.

Speed = 250kts Altitude = 9000ft Miles to go = 30nm

How are we doing now?

Looks similar to our first example, doesn’t it?

Are we?

HIGH

ON PROFILE

LOW

PLAY YOUR CARDS RIGHT

Are we?

HIGH

ON PROFILE

LOW

PLAY YOUR CARDS RIGHT

Spot the tail-wind!Any head/tail-wind must be accounted for in our calculations:

Height AAL 9000’ x 3 = 27Decel to 220kts 3 x 1 = 3Head/Tail wind (1nm/10kts) 3 x 1 = 3

33nm now required

Conclusion

• CDO approaches are beneficial in terms of noise and efficiency

• CDOs require thought – advise crews they are required!

Conclusion

Conclusion• CDO approaches are beneficial in terms of noise and efficiency

• CDOs require thought – Advise crews they are required

• Essential components to fly a CDO

1. Accurate track miles from ATC

2. Speed reduction to be considered

3. Correct rate of descent used

4. Wind conditions to be considered

Beyond the Flight Deck