Aircraft Performance
 

A question for aircrew and operations staff-do you believe your training in aircraft performance is or has been adequate and thorough? I'm doing some research on this subject and appreciate all feedback.

Thank you,

Jon Caples

Yes, no problems...on any of the several types that I have flown.

It depends upon the operator, and the culture.

My background is from the Australian Airline system where Performance knowledge was sacred, understood well by most pilots, and deeply embedded in the airline culture. I can say the same of some other operators whom I've observed - QANTAS (superb), Australian Airlines, Ansett, South African Airways, Indian Airlines, Lufthansa to name a few. I'm sure that there are numerous other operators who take Performance understanding amongst pilots very seriously.:ok: SOME DON'T.:eek:

It is my opinion that Performance UNDERSTANDING amongst pilots with my present employer is ABYSSMAL, and that's a compliment to them.

I will be the first to concede that application of performance data available, and application of company policy is very good, but deeper knowledge of the Performance BASICs is almost non-existant. They know how to do it, but don't know WHY.

When charged with doing the Performance Engineering for one of the company's subsidiaries, I wrote a Performance Training manual, I called it "Performance for Dummies". The company only showed luke-warm interest, but did publish it, and did programme 2 day courses on Performance basics for intake pilots with yours truly running it. This was well received, which surprised me a bit, it seems that the trainees did Performance 'A', got a tick in the box, and bulk erased the learning.

After I left that division, the Training Manual went out of print, and no more training courses were scheduled. Instead, a half day training of "How to use the Data" was introduced, no deeper understanding required.:ugh:

Now, I spend line flights with F/Os who ask never ending questions en-route about performance. They understand the HOW, but have a strong yearning to know the WHY:D

I'm usually a strong supporter of my airline, but, in this area, they stink.:mad:

It depends upon the airline, and it's culture!

Regards,

Old Smokey (who will be looking for a new job soon)

I just came from a place in which the performance calculations were the bailywick of the flight engineer. All crewmembers were expected to maintain proficiency and to demonstrate regularly use of the performance calculating programs and documents. Wise crewmembers always took it to heart that while the flight engineer might be a consummate professional, he may also make a mistake. Accordingly, we always verified what was given us. I always do.

I find with my current, temporary position, performance training given at the company level has been lacking. As a check airman and company instructor, I have an opportunity to correct that, and have been working hard to do so. I firmly believe all crewmembers (flight deck crewmembers, that is) should be 100% proficient and understanding in their approach to performance calculations.

It's important stuff.

Wow-Thanks for the response!
 

Thanks to everyone who responded! Let me take a look at everyone's responses then I'll come back with a short list of questions about performance. Again thank you to everyone who has responded and thanks in advance to those of you who respond to the questions that will be posted in a few days.

Everyone have a safe and success filled future!

Jon:)

You can just delete your double posting yourself.

Yes, training is thorough and complete, and set for the lowest common denominator.

And these are the reasons I try to wash'em out in ground school:*


Lester:E


:(

Questions will be posted within two days
 

Hello all,

Weekend didn't go as planned, spent most of it in bed with a cold so a little behind. I'll have the questions posted within two days. The answers should be fairly obvious and hopefully not too biased toward the FAA ways of doing things.

Looking forward to every one's comments as several of the questions should generate some discussion (they have when asked to other folks).

Have a great week all!

Jon :)

You have got to be joking me... :):) The FAA way of doing things doesnt teach you performance, you just have to remember the answers!

Mutt

Here's two samples...
 

Here's two sample questions to hopefully whet your appetite:

1-Which climb segment(s) is always most limiting?
A) Second Segment
B) Third Segment
C) Answers A and B
D) Not enough information or there is no correct answer given

2-What is the difference between clearway and stopway?
A) There is no difference, other than one is at the arrival end of the runway and the other at the departure end
B) Clearway must be paved
C) Stopway must be as strong as the associated runway
D) Not enough information or there is no correct answer given

Back tomorrow with more... :ok:

Jon

D and D. Did I pass?:confused:

Regards,

Old Smokey

Here's eight more for a total of 10 questions...
 

3-Maximum weight for take-off is always the ____ of runway limit weight, climb limit weight, obstruction limit weight, and maximum structural take-off weight.
A) Largest
B) Least
C) Greatest correct for temperature, field elevation, and wind
D) Not enough information or no correct answer given

4-Maximum structural take-off weight varies with?
A) Temperature, field elevation, and altimeter setting
B) Flap setting and wind
C) All of the above
D) Not enough information or no correct answer given

5-Using more flaps/slats for take-off will?
A) Increase ground roll and increase climb gradient
B) Decrease ground roll and increase climb gradient
C) Increase ground roll and decrease climb gradient
D) Decrease ground roll and decrease climb gradient

6-Since we know performance figures (weights and speeds) are conservative it is ok to take-off or land as long as our weight and planned speeds are close to the calculated figures.
A) True
B) False

7-How much climb capability is lost after one engine on a twin engine aircraft fails?
A) Less than 20%
B) Less than 50%
C) 50%
D) More than 50%

8-Airport AAA has three parallel runways all oriented 13/31. 31L has 11,150 feet available for take-off, 31C has 9,750 feet available for take-off, and 31R has 9,500 available for take-off. 31R has the largest take-off weights, why?
A) Dispatch didn't calculate the weights correctly.
B) The other pilot or engineer didn't calculate the weights correctly.
C) Poor take-off technique.
D) Obstacles

9-Using maximum engine thrust for take-off will always result in larger take-off weights?
A) True
B) False

10-Obstacle data obtained from two different vendors will match.
A) True
B) False

Hope this sparks some discussion and thought. I'll post answers and short explanation Monday 5/18.

Jon :ok:

Seejonfly...

What are you attempting to achieve?? This isnt a wannabee forum !!

Mutt

because performance is so complicated a subject,...all of these questions have more than one possible answer depending on the day,...for example the second segment is normally limting,...but not ALWAYS:=

so these are all ambiguous questions and I go with my friend OLD Smokeys' answer,...
D and D

and yes I know what the FAA is looking for;),..but their books are not detailed enough for this field the FAA books are for pilots,..but this subject is immensely complicated that neither the AIRPLANE FLYING HANDBOOK,. or PILOTS HANDBOOK Of AERONAUTICAL KNOWLEDGE ,...cover this subject entirely nor Gleim nor Jeppessen,.......

PA

Hi Mutt!
 

My goals are:

1-See if there is enough interest in this topic to continue a business built around providing aviation training and engineering services especially in the area of performance but also including CRM and some other allied topics. And I promise that I will not hound anyone who responds to the quiz with solicitations...in fact I won't solicit anyone on here. If anyone is interested in discussing business please send an e-mail to [email protected] . If this violates any of the rules of this forum I apologize and will take corrective action.

2-Plumb the level of knowledge about performance demonstrated by those who respond to the questions. Frankly, my experience has shown that very few pilots really understand performance. When I was flying professionally I thought that I had a really good understanding of performance. What I found out after working as a performance engineer is that I had very little understanding of performance....and a lot of what I had been taught was either missleading or downright wrong. I knew how to run the numbers but really did not understand what they meant nor how they had been derived. And, I'd say this is true of most pilots.

3-Hopefully, provoke some thought and spirited conversation about performance.

4-Have some fun with all this!

Quickly my background includes teaching ground school and maintaining ground school programs for a major US flag carrier, CAPT and FO at commuter airlines, 5,000 hours total flight time, formal performance training at Airbus and Boeing, and multiple years experience as an Aircraft Performance Engineer. Along the way I've acquired a lot of experience in several engineering disciplines along with graduate and undergraduate degrees in engineering.

Best to all! :ok:
Jon

Well you've been responded to by two top performance experts,...but this is kind of basic performance for what gets discussed here:ok:

we are not babies:ooh:

PA

Thanks for the feedback!
 

Based on prior experience thought it best to start simple. Please don't think I mean any disrespect or don't believe there are some really knowlegable folks on here (friend who recommended this forum to me is one of the sharpest guys around). I'll come up with some more challenging questions over the next few days. If anyone else would like to contribute some questions please do! :cool:

Here's a quick few:

11-Why might take-off performance be better from a wet runway than a dry one with all other conditions and the aircraft unchanged?
A) It can't be, performance from a dry runway is always better you ninny :) !
B) "Wet" conditions change the screen height from 35 feet to 15 feet.
C) "Wet" conditions can allow credit for the use of reverse thrust.
D) B & C.

12-The take-off performance data associated with an engine failure derived during certification testing are based upon?
A) An engine failure at V1.
B) An engine failure at V1-5 knots.
C) The aircraft remaining within 35 feet of the centerline.
D) A & C.

13-A given aircraft aircraft is certified under several different regulatory schemes (i.e. FAR, TC, EASA, and CAA-UK) with no changes to equipment. Its performance will be exactly the same except for minor differences caused by conversion to different units of measure (knots to Km/hr, KG to LBS, etc.)?
A) True
B) False

14-Your company owns and operates three identical aircraft (even the empty weights are the same...a miracle for the purpose of this question). One of the aircraft has a different AFM (Aircraft Flight Manual aka Approved Flight Manual) and higher take-off and landing weights (including maximum structural take-off and landing weights). Can this be correct?
A) True
B) False

15-Briefly explain why your answer to 14 is correct. I'll provide my answer Monday when I post answers to the existing questions and also a few more complicated questions.

Best to all, :ok:

Jon

11: A
12: C
13: A
14: A
15: We paid for higher weights!!!

Problem with asking this kind of question is that the answers are ambiguous :):)

11: Takeoff performance software has a DRY CHECK function, so from a pilots point of view he wont see higher weights on a wet runway.

12: Engine presumed to fail at VEF.

13: Different certification requirements, just try asking about crosswinds :)

14/15: Money talks......

Have a good weekend.....

Mutt

As far as A A subjects, I always insisted on reviewing the performance theory i.e. FAR 25, and FAR 121. It often happens that while pilots are perfectly able to read a performance table or graph, the detailed knowledge of performance concepts is lacking...
xxx
Personally, when I was flying, I made a difference between "hard limits", such as takeoff distances... i.e. runway length which is "physically limiting", and say a "second segment climb limit", which might be open airspace and in practice non existant obstacles...
xxx
You will not crash if you pass the end of the runway at 25 feet AGL, although performance on takeoff is based on passing the end of the runway at 35 feet AGL... So... performance - Know the meaning of the numbers you read on tables and charts.
xxx
:8
Happy contrails

it all depends,...from a C172 to C5

PA

hope your day is better than mine
 

Hello all,

Yesterday I was rear ended by idiot paying more attention to her cell phone conversation than her driving. Will posgt answers and explanation plus answer the private messages fro, inbox when I feel better.

Jon

Hello all! Holy cow muscle relaxants are wild!
 

Well since last post live for me has been wild...had to stop taking muscle relaxant doc prescribed because it really knocked me for a loop!

As promised here's some food for thought:

Sample questions and answer/explanation
1-Of the answers given D is correct. The second segment A is usually but not always most limiting.

2-Of the answers given D is correct. In addition to differences in allowable height of obstacles the other significant difference is STOPWAY must be able to support the weight of the aircraft during the stopping manuver.

Other Questions
3-B the least

4-D C is almost correct however as it, and none of the other possible answers, does not include obstacle data D is correct.

5-D more flaps will shorten take-off roll but also lessen climb gradient

6-B if you disagree I'd love to hear why

7-D Remember climb is determined by how much thrust is available in excess of that required to maintain level flight.

8-D I've seen this several times where parallel runways have different take-off weights for a given aircraft because of the difference in the obstacle sets.

9-A Although you do see this occassionally fom a strictly engineering perspective. Thanks to the Dry Check you should never see results that allow this to happen.

10-B Due to differences in how vendors select obstacle data to be reported and data sources there can be pronounced differences in data for the same airport from diffferent vendors.

11-A but perhaps not for the reason(s) you think. I've seen engineering analysis for the B757 (forgot engines used) where you could actually get better weights at reduced thrust off of a wet runway because with lower thrust there was a lower VMCG. But the dry check eliminated this from results sent to customer...but sure had us scratching our heads until we ran the problem with an engineering output!

12-C Most performance data testing is done around a range of V1s but regardless of the actual speed the aircraft (under FAR and most certification schemes) must be kept within 35 feet of the centerline without using nosewheel steering.

13-B Actually it depends upon the AFM you purchase. There are differences between all of the regulatory schemes which can result in different weights and speeds for the same aircraft/engine/brake combo.

14-A As several folks have commented, sometimes all you need is to pay more to get heavier weights!

Please feel free to comment on here or send me a personal e-mail. Hope this has stirred some thought!

Jon :D

Sorry to hear about the car crash..:( Hope that you have recovered.

I believe that you will find that in your 757 example the increased weight was due to lower screen height and use of thrust reverser for stopping, not a different VMCG as you don’t have contaminated/dry VMCG’s. :):)

If you compared different ratings, then you might get better contaminated weights with a lower thrust ratings depending on the runway length, we do this all the time to get out of JFK, the wet check just stops the benefits of the screen height/thrust reverser credits :)

Mutt

Hi Mutt, thanks for your comments!
 

Hi Mutt,

Thanks for your comments! I hope this thread has been interesting and thought provoking, if not please let me know. If anyone has some questions send em!!

Actually the improved performance off of the wet runway with reduced thrust was due to a difference in VMCG. Until I saw it I would not have thought this would happen. However if you think about it what happens to VMC with lower thrust? Think about it, with less thrust you will encounter less yaw due to assymetric thrust. I wish that I had kept some copies of the runs we performed while working on this...but I didn't and don't have a way to duplicate them now.


Jon

Seejonfly, sorry I've been too tied up in personal matters to look at pprune,...I perfectly understand the stupidity of ground vehicle drivers:*,..so I hope all is well get better

now back to business

---in my view many of these items have been discussed thoroughly on pprune in the context of various operational problems encountered by pilots regarding performance however in light of the teaching and performance engineering aspects [and I'm in 100% agreement that it needs further exploration in flight training curricula], I'm not saying it's not worth discussing again and again,...and the question you've submitted to pprune are exactly some of the issues that need to be explained much better and currently pilot texts fall hopelessly short ---even the 'official' FAA stuff---of approaching the subject correctly,

Mutt, Old Smokey, and John Tullamarine are all experienced performance engineers; who I'm sure share your concerns [I'm not but I'm no slouch with the subject:8] and perhaps a search of Pprune will be highly enlightening as to the type of questions that pilots generally ask

but, also I'm sure that the aforementioned gentlemen would be glad to direct you to areas of this vast subject that tend to cause operational confusion

but from my experience and education gained from Pprune they mostly concern
1. the segmented takeoff wrt to runway geometry
2. obstacle clearance and OEI flight paths [engine failure charts/procedures]
3. the derivation and limitations and uses of operational speeds V1, VR, V2
4. derated and FLEX or ATM takeoff
5. wet and contaminated runways
6. the limitations of FMC derived speeds
7.the Unbalanced field [which relates to item 1]

again sorry for the delay, I hope the accident was comparatively minor, and of course feel free to PM me if you wish

PA