Thrust reduction altitude

[Tee Emm]

Normally the runway analysis published flap retraction (level flight acceleration altitude) height is based upon an engine failure at V1. That is aircraft still on the take off roll. In fact some aircraft can have a spread of 25 knots between V1 and VR.

If an engine failed after becoming airborne then the published flap retraction or acceleration altitude is no longer a performance issue - although for standardization reasons , there is nothing to stop you using that published figure.
If the engine failed by coincidence just at the same time as normal two engine climb thrust was selected, (which could be at any height above say 400 ft), there is still no problem as the two engine operation up until climb thrust is selected would place the aircraft well above the net flight path calculated by the runway analysis. How much above depends on many variables but certainly safely above by several hundred feet of altitude.

Be careful you are not speculating "what if" when the problem you imagine does not exist. Too many "what if's" can only lead to unfounded fears of the dark, so to speak

[99jolegg]

The Airbus minimum you can put in the THR RED field is 400ft above runway elevation. The prescribed minimum from ICAO is 800ft.

The "Airbus - Aircraft Noise" document in section 6.1 "The Orange County Case" shows that unless you accept a hefty reduction in TOW to meet the noise constraint from runway 19R, you need to modify the cut back height of the typical NADP 1 procedure to 800ft and modify the climb thrust to achieve the minimum 1.2% gradient in case of engine failure, which is the minimum as per ICAO PANS-OPS.

So there is a case for reducing the cut back height below 1000ft in some cases, according to that document.

How realistic that is to most line operations I'm not sure; we don't modify the NADP 1 procedure.

[Intruder]

It's not just a simple decision. The company decided to set thrust reduction altitude at 800 ft , for a normal take off. And it used to be 1500 before.

You should then question them on the reasons for the change and the documentation behind the analysis. If they don't have it, "the company" is risking YOUR license and YOUR passengers' safety for an unsubstantiated change to procedures during a critical phase of flight.

It is POSSIBLE that the aircraft mfgr has given them documentation showing that the procedure meets certification requirements under the worst-case scenario. If so, they will be happy to provide that documentation.

"The Orange County Case" shows that unless you accept a hefty reduction in TOW to meet the noise constraint from runway 19R, you need to modify the cut back height of the typical NADP 1 procedure to 800ft and modify the climb thrust to achieve the minimum 1.2% gradient in case of engine failure

First, don't take an example out of context. The FIRST sentence in that case is:

CAUTION: It must be underlined that the noise level optimization must be considered as particular to each airport.

Also, it applies ONLY to the A319 used in the example, though it appears that Airbus has done the analysis and has likely provided the relevant documentation to their operators for other Airbus types.

If flying out of John Wayne, follow the procedures in the John Wayne Airport GA Noise Abatement Guide:

Safety permitting, pilots are encouraged to follow the aircraft
manufacturer’s recommended noise abatement procedures on all
arrivals and departures.

So, unless you have mfgr documentation to the contrary, follow standard procedures.

[framer]

If they don't have it, "the company" is risking YOUR license and YOUR passengers' safety for an unsubstantiated change to procedures during a critical phase of flight.

I don't see how they are risking licences or safety.

If the worst does happen, they set climb thrust at 800 feet, engine fails at 801 feet, they are 199 feet below acceleration height. Climb to that and accelerate. I can't see how it is either illegal or unsafe. It may be a fraction less safe, but not unsafe.