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Evan Banalian

Where to find preformance data for ngx

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Hello everyone, a Freind of mine who is a co pilot on

747 has an interview to become a captain on 737-8

And he wants to come check my sim and get more familiar

With 737 before going to the interview, now the question

They gave him an airport with 8300 ft elv

And 42c and he has to maintain 6.5 gradient

With one engine, v1 cut.

Now as fad numbers is there any preformance data, that I can provide him

So it can help him calculate preformance.

Dose pmdg provide any of these information ?

Thank

 

Evan Banalian

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The manuals structure in the 737 is the same as in the 747, so he should know his way around QRH, FCOMs, and, if supplied by company, FPPMs (not distributed with the NGX).

 

Now this information specifically.... I am afraid is not included. Who uses gradients for departures anyway? There are obstacle limits, but those are defined by obstacle height and distance from brake release, not by gradient.

 

Plus that is almost ISA+44. That might be a trick question, I am not sure operation in such temperatures is even allowed. I recall seeing somehting about ISA+40 or ISA+39 limit for the 737. Might be wrong though, although more things point to that, like not including OEI GA gradients for more than ISA+40.

Either way I call insufficient information. Even if this was a real scenario to be possible and to be considered, he will want to use improved climb technique. He will not get anywhere without field length, to know how far he can adjust.


--Peter Fabian 
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Who uses gradients for departures anyway? There are obstacle limits, but those are defined by obstacle height and distance from brake release, not by gradient.

 

Hi Peter,

The FAA requires that Climb Gradient with on one engine inoperative must be accounted for in takeoff performance.

Transport Category Aircraft are certified under Title 14 of the CFR Part 25. The airworthiness certification standards of part 25 require proven levels of performance and a guarantee safety margine. These include; Climb performance expressed as a percent gradient of climb, full temperature accountability, change in lift-off technique and performance requirements so that all transport category aircraft are operated under the same performance criteria.

Climb requirements require after an aircraft has reached a 35 foot height with one engine inoperative, there is a requirement that it be able to climb at a specified climb gradient up to 1500 above the ground to the beginning of the enroute segment.

Climb gradient can best be described as being a specific gain of vertical height for a given distance covered horizontally. A 2.4% gradient means that 24 feet of altitude would be gained for each 1000 feet of horizontal distance across the ground.

There are four segments in the climb profile. For two engine airplanes like the 737, the first segment is from lift-off to a 35 foot altitude and requires at least a positive rate of climb. The second segment starts at 35 feet and ends at 400 feet AGL and requires a minimum of 2.4% climb gradient. This segment is the most critical segment with the steepest minimum gradient due to flaps extended. The third segment communally called the acceleration segment, starts at 400 feet AGL and ends when the flaps are fully retracted. The airplane is accelerated from V2 to flaps up climb speed and the climb profile is continued. This segment only requires a positive rate of climb. The fourth or final segment starts when the flaps are up and established in a clean climb profile and ends at 1500 feet AGL and requires a minimum 1,2% climb gradient. The airplane is now in the enroute phase.

 

Obstacle Clearance Requirements are another ground school lesson.........


John Floyd

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John, I am aware of the 2.4/2.7/3.0 gradient requirement.

However, the question as it stands mentions 6.2% gradient climb... which I would say is most unusual to consider for a standart departure calculation. In any case I have not been able to find takeoff gradient info even in FPPMs. I would go as far as to say that this kind of data is not available/calculated further than "this weight will assure the 2.4% (and 1.2% in fourth is it?) climb gradient" and "this is how you may use improved climb if so needed".

Meanwhile obstacle clearance is calculated on the basis of distance from brake release, which is not quite the same as gradient, although I guess, with knowing the place of liftoff, or maybe better second segment entry, such obstacle as to assure 6.2% gradient could be approximated.

 

With the data given - in QRH, FCOMv1 and FPPM - the closest thing I could get to was missed-approach gradients at flaps 15. But even leaving the fact those might be misleading and suboptimal (lower flap departure might be possible, yielding better results), they still do not cover ISA+44C.


--Peter Fabian 
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However, the question as it stands mentions 6.2% gradient climb... which I would say is most unusual to consider for a standart departure calculation. In any case I have not been able to find takeoff gradient info even in FPPMs. I would go as far as to say that this kind of data is not available/calculated further than "this weight will assure the 2.4% (and 1.2% in fourth is it?) climb gradient" and "this is how you may use improved climb if so needed".

 

Peter, sorry I ground schooled you unnecessarily, but maybe some of the other forum members will benefit.

This airline his friend is looking at probably operates under a supplemental certificate, and at an airport that has a runway which requires a minimum 6.5% climb gradient with one engine inoperative to operate off of safely.

You know, bottom line for me is flight crews shouldn't have to do this kind of thing anymore. With full dispatches and airport/runway analysis performance data common place now, there's no need to calculate stuff like this anymore. Really! I wouldn't work for any outfit that was going to make me calculate my own performance data! It's definitely a thing of the past!

Better stay in the 744.


John Floyd

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Not at all John, there was a time I thrived on reading any such discussion. I am most pleased to be able to give something back.

 

What with you mentioning supplemental certificate - a good point, that. I was thinking along those lines, but not exactly. In any case I feel that airline is obliged to provide neccessary data if this kind of operation is expected, in its own manuals...


--Peter Fabian 
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Thanks everyone, we tried this on the sim, and there was no way for the airplane to preforme well in that kinda condition, As far as the ngx gose my friend was amazied with how accurate the ngx flies, systems, etc and he was kind a jealous that now we can do all this at home, the only issue he had with the rudder being too sensitive compared to real 747, 737 airplane.

Thanks pmdg for making this possible.

 

Evan

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Really! I wouldn't work for any outfit that was going to make me calculate my own performance data! It's definitely a thing of the past!

I agree, I actually find the whole story completely fishy.

If he was working for some outfit flying DC-3 I might see the point of such exercise but someone flying 737-800 being asked to calculate this sort of things is to me an indication that something is very wrong in this whole story. Also who on earth would ask such question knowing from start that it was impossible, I agree that could be a 'gotcha' for a rookie PPL pilot but not a 747 copilot. And the numbers (8300 ft, 42C :shok: ), no weight given (poorly defined problem), even a mere PPL like me can suspect this is an impossible scenario, a real 747 copilot would not be coming to his simer neighbor for 'consultation', sorry I find this whole story completely ridiculous.


Michael J.

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One correction, the temp that was given 17c,

My friend is a co pilot on 747 with only 300hrs on the 747, 7000+hrs on EMB-145, and will go for interview for

737 captain job, and they gave him these numbers and approach for SKBO, Don't know the whole

Story, but you are funny how u don't believe the story

As if I asked for donation help form you.

 

Evan

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Don't know the whole

Story, but you are funny how u don't believe the story

Well the question didn't make sense with the temp 42C. Anyone who knows the plane would look at that question and think there's something wrong going on. I've got the AFM, I'll look when I can to see if that can be done.

Matt Cee

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I don't have -800 numbers. I can find some -400 numbers, but you still need a TOW to find the answer. The "spaghetti" charts are rarely used in scheduled service. Unless the company is going to give your friend some runway analysis to work with, the question seems odd. You could just say 6.5 is a pretty high gradient for a normally loaded plane. Maybe on a ferry flight.


Matt Cee

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Now Evan it makes MUCH more sense...

 

So ISO of ISA +44 we are looking at ISA+19 (which would make 44C at sea level, I see where the mistake was made), and ISO V1 cut we are looking for OEI go-around I believe.

 

Now that is comparatively easy to figure out, provided your friend has the FPPM from his airline.

Anyway I took what FPPM I have access to, and took the chart for OEI G/A gradient. Please note this is not FPPM tailored for his airline and it may yield different results.

 

well anyway with approach at F40 Vref+5 and bleeds on, I came to a max weigth of about 45 tonnes... I reckon there is a couple hundred killograms to get from doing a F30 approach, bleeds off, and so, but with 737-800 typical DOW of 41t+, hardly enough to get any meaningful load into her...


--Peter Fabian 
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Since the question referred to a V1 cut, I assume it was a takeoff case, not a go-around. Although flaps 15 is both an approach and a takeoff flap setting, the speeds for takoff climb would be different from those for approach climb. Also, if it is only a gradient capability consideration, a lower takeoff flap setting would give better performance.

 

Still, the question as presented does not contain enough information in that it does not specify where in the takeoff flight path this gradient must be achieved. Unless the pilot has access to the computerized airplane flight manual or his operator provides him with the data, he's not going to be able to answer this question. This type of data is not provided in the FCOM, FCTM, QRH, or FPPM.

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