High/Low 3rd sector accel - Safe?/Unsafe?

[G-SPOTs Lost]

Hi there,

Currently in a "discussion" with somebody about acceleration altitudes and achieved climb gradients.

Consider an bizjet certified in yr 2000, with a published accel altitude of 1000ft AGL. It would appear that we are being told to climb at V2 until accel altitude or chart MSA whichever is higher(which invariably is higher than 1000ft!).

I'm personally not too happy about this, surely if we are being asked to climb to 7000ft for example (In europe) in a dirty configuration at say 115-120 knots (V2) then there is no way we are going to achieve published climb gradients and could well end up hitting the piece of granite we are trying to avoid.

I personally am advocating (In the sim scenario of a Engine Failure just after V1) of a "close in" sector three acceleration of the 1000ft published figure and cleaning up and accelerating to 150 VENR and achieving a better gradient.

So the question is even though you know the terrain is out there, do you do what feels good and leave the flaps where they are or have faith in the manufacturers figures and cleanup/speedup earlier.

I personally favour the latter but am getting a lot of adverse grief from more experienced/greyer people who have been doing the job a long time, I'm more than willing to doff my cap etc and be proved wrong.

More info:

In fairness lets assume its a UK Jar Ops AOC holder doing ad - hoc charters and doesnt have access to surveyed obstacle data for an airport you only found out you were going to 2hrs before.

In rough percentage terms just how much gradient do you think we are losing by using the unofficial procedure (Difficult to quantify but a rough guess will suffice)

Thanks for your advice chaps

[PantLoad]

The thrust-reduction/acceleration altitudes are not a certification issue...They are determined by the operator (within limits). Therefore, your company is free to establish an SOP which requires sensible or goofy altitudes/procedures (your management's choice).

However, "MOST" operators consider the following:
(This list is not exhaustive.)

1. A minimum altitude so as to ensure positive control of the aircraft. (Don't do anything below this altitude, because you're too close to the ground, and you shouldn't be screwing around doing anything BUT FLYING THE AIRPLANE!) 400 feet is a common figure to satisfy this requirement.

2. A minimum altitude that provides terrain clearance, both in the event of a normal (all-engine-operative) and an engine out (one-engine-inoperative) scenario.

3. Satisfying noise abatement requirements...both general requirements and airport-specific requirements. For example, your company may adopt ICAO A or ICAO B profiles as SOP. However, there may be published exceptions in your SOP that are airport-specific.

4. Time on the engines where they're operating at a thrust level above MCT. Economics and engine manufacturer limits apply.

Again, the four above-listed points are not all the considerations. I am not knowledgeable enough to get more specific and into more detail. There are other participants in this forum who have forgotten more than many 'experts' will ever know.

Typically, most airlines/operators choose 1000 feet to 1500 feet as the thrust-reduction altitude. The acceleration/clean-up altitude varies with operator, the ICAO A or B procedure, and specific local airport requirements.

ICAO A calls for initial climb at takeoff thrust (either TOGA or FLEX) to 1500 feet at takeoff flaps and V2+10 to V2+20, then the thrust reduction to climb thrust. Then, the aircraft is flown with climb thrust, and the takeoff configuration is maintained (V2+10 to V2+20) to 3000 feet, where the nose is lowered and the airplane is cleaned up.

"Enroute Climb" can then be established at that point...which can be defined by the operator. For example, some SOPs say you can go to 250 KIAS, while others say you need to stay at best angle of climb (clean, all engines operating) until clear of obstacles, at or above the MEA, clear of noise sensitive areas, etc., etc. (Management can define this as they wish.)

The ICAO B procedure is similar, except the clean up and acceleration occurs right after the thrust reduction. Maintain best angle (clean speed with all engines operating) until 3000 feet, then....."Enroute Climb" speed as discussed in the above paragraph.

Again, these different procedures (the ICAO A, the ICAO B, or whatever management decides to call their SOP) are designed to minimize noise, assure terrain clearance, save engine wear, minimize crew workload at critical times during the takeoff, etc.

But, I've never heard of holding takeoff flaps and V2 until at or above the MSA, MEA, or the like. I suppose you could do it...as long as engine limitations are observed. But, I fail to see the 'big picture' in doing so.

Standard Instrument Departures (or DPs...as they're now called in the U.S.) have specified required climb gradients...either a generic standard, or a specified published minimum tailored to that airport and departure path. Your manufacturer can provide performance data that will guide you with regard to takeoff wieght limits to achieve the necessary gradients.

It may, in fact, be necessary to provide a single-engine departure...in the event that the SID's gradient is too steep for your aiplane...based on weight limits, etc. Again, this is the task for your management people.

In cases where there is no SID, your management is saddled with the task of determining what obstacles exist, where they exist, what departure procedures are prudent (your company's SOP...after consultation with the manufacturer and their published performance figures). Takeoff weight limitations can then be imposed to ensure adequate gradients in the case of all engines operative and one engine inoperative.

Why re-invent the wheel! Suggest to management that they see what other operators are doing. Consult the manufacturer. Develop an SOP that is based on research done by others. ATC can help in suggesting single-engine profiles (based on what other operators are doing)....this, in concert with your manufacturer's recommendations. Again, it's management's responsibility to do all of this.

In the end, you are legally bound to follow your comapny's SOPs. Good luck, we're all counting on you!


PantLoad

[G-SPOTs Lost]

Hi there from the AFM

Paraphrased until relevant


SINGLE ENGINE TAKEOFF - ACCELERATE GO

a. TO Power set static - brakes released
b. recognise engine failure V1
c. positive rotation.....V2 by 35ft
d. positive rate gear up.

e. "V2 was maintained from the 35 foot point above the runway to 1000 AGL"
f. "The airplane was accelerated to V2 +10 KIAS at which time the flaps were retracted and the acceleration continued to VENR. Power was reduced to the climb detent and the climb continued"

My point is this method was used to achive the book climb gradient figures if we leave the airplane in this initial dirty configuration until MSA then the "book" figure will not be achieved - safe/unsafe? or just not prudent

We have 5 mins MCT or 10 mins MCT single engine

Thankyou for the thorough reply

[PantLoad]

Your concerns are valid.

PantLoad

[BizJetJock]

This is quite a common procedure in the market you're talking about, since most operators don't want to fork out for a proper runway analysis for each trip - apart from the short notice time constraints.
As to it's advisability, there are two factors here.
1. Your a/c may or may not have figures in the manual for extended climb. Certainly the CL604 does and the 601 doesn't. If it does you can use those to get an accurate figure for speeds/gradients up to whatever accleration ht. If you haven't extended climb figures then you need to use the speeds and gradient for the end altitude, which is conservative. Either way it not a certification problem.
2. Look up the distance required to accelerate OEI at high weights, and then decide if you want to fly around below MSA in cloud in an unfamiliar area for that number of miles!
After that I think you'll find it's the sensible option:ok: