Thought process: Best angle or Best Climb rate

[extricate]

Hi,

I know the diff between Best angle and Best rate. One relates to highest amount of height in a given distance, the other relates to height in a given time.

Say, out of HKG on runway 07, what's your thought process of retracting flaps? My thought is that I will want to clear obstacle for a given distance (Flying as close to best ablge), that means I will delay retracting flaps, and will only start cleaning up after the turn to the right.

Just curious about your thought process

Thanks

[AerocatS2A]

Your question assumes that climbing with flap gives a better angle than clean. Are you sure this is true for your aircraft?

[vilas]

Why would you do that? The gradient requirement of 4.9/4.1% is only to 1400ft. After that there is a minimum speed requirement of 180ks. and Max altitude of 5000ft at the turning point Porpa/Rover. Follow normal noise abetment procedure 1500/3000 but restrict speed to 220kts as is required till next point after Porpa.

[RAT 5]

Apologies, not familiar with the SID. Have you a link; and do you start the turn at a DME fixed point or above an altitude/height?

[Vessbot]

Originally Posted by AerocatS2A

Your question assumes that climbing with flap gives a better angle than clean. Are you sure this is true for your aircraft?

Well, ultimately best angle is of course provided by a clean airframe. For maximizing height over a distant obstacle, that's what's necessary. By definition. But to get there, you have to reach flap retraction speed, which means flying a shallow climb angle for a while. If you're trying to maximize height over an obstacle located where that acceleration is happening, that would be worse than keeping the flaps down and flying the flaps-down best angle climb speed.

There's a break-even point (in distance from the runway) where height maximization changes from being best benefited by the short-range flaps-down speed-maintenance strategy, to the long-range acceleration and clean up strategy.

[Vessbot]

The first sentence is right, the second isn't.

OP (or anybody), don't let yourself be discouraged by this attitude. It's everybody's eternal task as an aviator to try to understand the mechanics of flight as best as you can; and, from that, why you do things the way that you do them.

[wiggy]

Apologies, not familiar with the SID. Have you a link; and do you start the turn at a DME fixed point

Rover or Porpa are Flyover waypoints (defined by a couple of DMES and lat long etc)...on the extended centreline for departures off the 07s at HKG..after crossing them you turn right towards the south basically out over the sea. As Vila’s has said the whole point of the position of Rover/Porpa is as long as go to them (and then turn) there isn’t really a major major climb gradient issue.....

The one thing not to do is turn south too early............. and not fly too fast until around th3 turn.

[Gauges and Dials]

Originally Posted by Vessbot

Well, ultimately best angle is of course provided by a clean airframe. For maximizing height over a distant obstacle, that's what's necessary.

Sidle up to a table full of pilots, engineers, armchair pilots, and wannabe-engineers and make that statement. Sit back and enjoy your popcorn as general hilarity ensues for the next hour or so.

Once you tire of that, you can ask a group of sailors to discuss whether a glossy finish or a matte finish on the hull is faster. You'll need a lot more popcorn.

[extricate]

Originally Posted by Vessbot

Well, ultimately best angle is of course provided by a clean airframe. For maximizing height over a distant obstacle, that's what's necessary. By definition. But to get there, you have to reach flap retraction speed, which means flying a shallow climb angle for a while. If you're trying to maximize height over an obstacle located where that acceleration is happening, that would be worse than keeping the flaps down and flying the flaps-down best angle climb speed.

There's a break-even point (in distance from the runway) where height maximization changes from being best benefited by the short-range flaps-down speed-maintenance strategy, to the long-range acceleration and clean up strategy.

Exactly, that's my consideration

Understand there's a speed restriction, below 220kts, by flying slower allows a better turn radius too

[B2N2]

Semantics but a smaller or lesser turn radius....not a better.

[vilas]

The example of HK 07 departure is not relevant to the topic of angle/rate of climb.

[Vessbot]

No, I'm suggesting that the majority of the time someone says to "not overthink it," it's due to a far too low setting of the bar of where "over" is, and actually they're underthinking it.

While this discussion sprang from a particular DP, the answer is underpinned by the general principles of climb performance involving thrust, drag, acceleration, etc. (from aeronautics specifically) and more general logical concepts like the break even point between zones where two different factors dominate an outcome, and maybe even a bit of trig; or, something requiring a "thought process," if you will.

In a strict sense the answer to what's to be done is to follow the company/manufacturer climb profile, but it's a safe assumption that Extricate already knew that, and was already doing that, as that's the procedure beaten into to all of us in training from day one. If that's the case then what he really asked was about the analysis of how these profiles are arrived at, in terms of the aeronautical principles mentioned earlier. So perhaps it is your interpretation and not mine that "missed the question." (And in post #10, he confirmed my hunch.)

[piratepete]

Firstly you must be RNP 1 qualified, meaning that absent any failures you will FLY OVER the initial waypoints, meaning that you will always avoid the high terrain, in this case to your right.However in general, due to traffic issues ATC will often ask to you to INCREASE SPEED to 220 knots minimum quite early, perhaps at first contact so any attempt to maximise your climb gradient is pointless.........

[Centaurus]

When I sit in the sim (or aircraft/jumpseat) and listen to some of the longwinded departure briefs about what the PF will be doing (this that and the other) during the departure and that PNF will tune this, call that, select his/mine ... you know the sort? Any how, throw a simple failure or fault in the mix (in sim) and it all goes to pot, PF can’t fly for toffee, or follow the required profile ... I wonder, for starters, why not start by just flying the sodding aeroplane!

Reminds me (going back 50 years or so) of when I was flying with my CO - a Wing Commander no less -and I was the co-pilot of the Convair 440 Metropolitan we were flying. He told me he did not believe in before take off safety briefings.
His point being that with an emergency, the situation can change with every second of the take off run and initial climb; and that he would decide on the spot what actions to take, only if and when, something untoward happened.

Re briefing a departure or arrival instrument approach charts, he said both pilots have eyes and can read the charts for themselves and shouldn't need to talk through the charts to each other. I am not saying he was right; but he was a man of few words and preferred general silence in the cockpit - unless of course essential communication between the two pilots was needed. He would surely turn in his grave if he could see or hear the babble of SOP briefings on todays airline flight decks

[RAT 5]

When I sit in the sim (or aircraft/jumpseat) and listen to some of the longwinded departure briefs about what the PF will be doing (this that and the other) during the departure and that PNF will tune this, call that, select his/mine ... you know the sort? Any how, throw a simple failure or fault in the mix (in sim) and it all goes to pot, PF can’t fly for toffee, or follow the required profile ... I wonder, for starters, why not start by just flying the sodding aeroplane!


Agree, agree. Been there, done that.

but why not just operate the aircraft the way the Company want you too?

Unfortunately because the 'longwinded brief' is written chapter & verse in the SOP's; even though there was also the laughable statement elsewhere saying, "briefs should be brief and not repetitive otherwise the listener will lose interest and forget what was said." Duh!

[Centaurus]

but why not just operate the aircraft the way the Company want you too?

Meaning the way the particular chief pilot wants you to, based on his personal opinion. When he moves on another new broom replaces him and his opinion is what counts now - etc

[safetypee]

The most important aspect of the thought process is to think about the issue before you encounter it in flight.

For the unseen, surprising encounters, good subject knowledge, well practiced disciplined thought; assess the situation and consider why a chosen course of action might not be correct, opposed to looking for confirmation.

[Centaurus]

don’t try reinvent the wheel, and just operate the aircraft the way the Manufacturer and the Company want you too?

Thread Drift from angles of climb, I know. In another life I flew for a small company that employed about 30 pilots. After problems experienced by some of the crews in the simulator, several of the braver types got together and complained to the Deputy Chief Pilot that each check captain used different SOP's for engine failure on take off. Please could they have decent standardisation between them (the check pilots).

The Deputy CP knocked on the door of the Chief Pilot and said the pilots had requested an audience with the CP to complain about check captain standardisation in simulator training. The CP was an impatient gruff type who had a reputation of being good with his fists. He ordered his deputy to march the pilots into his office, where he would sort them out.

When informed by his deputy of the nature of the pilots' beefs, i.e lack of standardisation among his check captains, the CP said that the company SOP's in regards to engine failure on take off were quite clear, and he proceeded to reel off his version of the relevant engine failure SOP in front of the upset pilots.

There was a moment of stunned silence as the deputy CP and all the pilots gathered there in front of the menacing CP. No one was game to speak.

Then with marked reluctance the deputy CP stepped forward and said: "Sorry to say this, Boss, but that's not what is in the company SOP manual."

The meeting was then closed and the pilots all filed out with grins on their faces. They had made their point.

[vilas]

For Airbus FBW it is straight forward follow the manufacturer. Any intended deviations should be referred to Airbus for their concurrence. Because unlike conventional aircraft in Airbus things like thrust levers, flap lever, LG lever provide inputs to different computers which have bearing on aircraft behavior. It is not possible nor is it required to to know everything. Take manufacturer's opinion and leave it at that.

[vilas]

I am really curious about OP's thought process in selecting HK 07 where you only need 4.9/4.1% gradient to 1400ft. When any 50 degree flex takeoff with noise abetment 1000/3000 will give minimum 9 degrees gradient no special thought process was required. So all the discussion was a drift.