RTOW

[ElNull]

Using the RTOW chart (for a specific runway) at a given temperature, how do you know if you are Obstacle/Field Limited or Climb limited? Which weight of both should you consider?

[CaptainProp]

Not sure if I understand your question correctly but generally you have to use most limiting weight.

[Piltdown Man]

Your perf. table will print a little code letter or in words describe your limiting factor.

[BOAC]

Which a/c?
Which performance provider?

Have you done a performance course or are you an 'enthusiast' with a performance page? Where do we start?

It would help to reproduce the page (or some figures from it) here.

[ElNull]

Here's an example I found of the RTOW: http://i60.tinypic.com/15y9e6o.jpg

At a given temp. You have two limited weights, climb limited weight and obstacle/field limited weight. Which one of those would be your performance limited weight?

[BOAC]

Well, you still have not answered the questions, but you can read? *=Obstacle

The answer to your second question in post 1 is THE LOWEST OR 79015.

[ElNull]

BOAC, During windshear take off precaution, B737 manual suggest to increase Vr to the "performance limited" gross weight rotation speed, not to exceed actual gross weight Vr+20 knots.

So my question here, using the RTOW I posted, you should check the OAT to get the limited gross weight? Now, you have climb limited weight and obstacle/Field limited weight. Should you consider the lowest weight of both? (Which usually be the climb limited weight in the chart I posted?)

And with the Antiskid inop, using the RTOW chart, you would use OAT to get the Obstacle/Field limited weight to remove 7950kgs. Correct?

[BOAC]

Well, you still have not answered the questions - and this is getting silly.

Of course it is the 'lowest' weight or you will exceed a limitation.

On 'windshear' you do not appear to be asking a question?

As for 'Antiskid inop' - I do not have the figures, but you seem to?? The answer is 'possibly'.

I am not prepared to waste time any more on this thread. Good luck.

[ElNull]

In the b737 you have a limitation with anti skid inoperative to remove 7950 from the obstacle/field limited weight.

Question: how would you do that with the RTOW chart I posted?

From b737 supplementary procedures (for windshear precautions) "Consider increasing Vr speed to the performance limited gross weight rotation speed, not to exceed actual gross weight Vr+20 knots.

Question 2: how to know my performance limited weight (field/obstacle/climb..)? Can you give me an example with the RTOW I posted?

[+TSRA]

If I understand your question properly, you simply take the obstacle weight given by the data and subtract your figure from that. I've not used the type of performance page you linked - only Aerodata or APG - but it appears the first number is your take-off weight divided by 100 (followed by your V-Speeds).

So simply multiply the weight figure by 100 to get your allowable take-off weight and then subtract your performance restrictions from that...for example if you read 792 as the figure, that's 79,200 kilo for take-off subtract your 7,950 from that giving an actual allowable take-off weight of 71,250 kg (roughly 159,600 pounds). Any 737 pilot might want to clean this up if I'm in error though.

As for your question about Obstacle or Climb Limit weights...you'll have to take a performance course, but as simply and roughly as I can a Climb Limit does not take obstacle clearance into account - it means that you can take that weight off that runway and still climb (on all engines). Obstacle or Field Lengths take that obstacle clearance into account (on one engine), hence the reduced figures.

So, operationally...if you assume obstacle clearance you can take the Climb Limit weights...if you want to make sure you can climb away, use the Obstacle/Field charts...in other words, VFR/IFR.

That was horribly rough and does not do a service to all the information behind that sketch. I would suggest you Google "Flight Manual Performance" or "Pilot Guide to Takeoff Safety"...both are good starting documents.

[de facto]

Right,,
The weight is an addition to your regulated take off weight for use of ass temp.
For example low pressure,you add to your actual tow to get your new regulated weight and then you find your max ass temp.
Concerning anti skid inop..you need to reduce your field/obstacle limit weight where the speeds are written.(you enter your rtow chart with actual OAT )and the weight where speeds are is your field/limit ,you substract 7950kg and it becomes your new dry field limit weight.
Then you need to correct your dry field V1 by an amount givenin your fcom based on field lengh required that you find in your dispatch perf manual..it should be about -12 kts or so.

For your initial question,as you enter your rtow table from left to right with OAT,you will see two weights,left column(climb limit) and rest(with speeds displayed) is the field/onstacle limit weight.
Your regulated take off weight(actual weight regulated for low pressure,wai,tai...) as you go up the ass temp becomes limiting when higher than climb or field/level off..
The highest mass with a reg weight below or equal to either lowest of climb/field becomes your max ass.

Your min ass in the other hand is based on your engine thrust tref.

[ElNull]

Thanks de_facto

You got loadsheet and got the actual gross weight, assuming you will use RTOW chart to get your speeds and assumed temp. (With regardless to EFB)

Now using the actual gross weight, which limiting weight you should use to get the related V speeds? Climb (first column) or obstacle/limiting weight

[Capt Chambo]

...which limiting weight you should use to get the related V speeds? Climb (first column) or obstacle/limiting weight..

You use your "Field Limited Weight", (not your climb limited weight).

Ref. Boeing Flight Planning and Performance manual, Takeoff and landing text

[JeroenC]

I was taught differently, Capt Chambo (ref: we actually use these tables). Einull, u take the lowest of climb (most left column) and the limit in the right column, which can be either: field length limited, obstacle, max brake energy or max tyre speed.

[ElNull]

Thanks jeroenc. But in this case (according to the RTOW chart I posted) I will always use climb limited weight because it is always lower than the obstacle/field...

[JeroenC]

Have a good look. Eg OAT 30 degrees, climb limit 83,6 tons, obstacle limit for nil wind: 78,1. So you are obst. limited, hence using 148, 151, 157 as speeds.

[Capt Chambo]

Unless you use an electronic performance based calculating tool like a BLT, OPT, or you tabular presentation is different to the standard Boeing presentation, then with Anti-Skid inoperative, you use the normal dry field limit and obstacle limit weight.

I include a link to the Boeing 737(800) Flight Planning and Performance Manual which I found off the net. The relevant text is in section 1.1 Takeoff and landing text, P20/294. This is a 2006 version and it is the same as my initial Boeing manual dated 2000 as well as my current performance manual dated 2010.

Hope this helps



http://hildalarrondo.net/wp-content/...nce_Manual.pdf

[ElNull]

Oh Sorry about that jeroenc... I meant the obstacle/field is always lower than climb limited weight (in the first column) so I would always use obstacle/field weight (perhaps this is what capt chambo meant)

[JeroenC]

Ah, sorry Capt Chambo, misread your answer. You were referring to the antiskid INOP. Our tables only list the most limiting of the options and that's where we reduce a fixed (most conservative) anti skid inop penalty from. If that's too limiting, call OPS The table and penalties work nicely during short turnaround times, but are very conservative.

[Capt Chambo]

My reply(s) were in relation to the question about Anti-Skid inop. and how you apply the weight and V speed corrections.

Otherwise I believe that the original question has been answered, in that you take the lowest weight from either the Climb limit column, or the Obstacle/Field limited column. (NB from the Obstacle/Field limited column the actual maximum weight may be limited by field, brake energy, tire speed limits or Vmcg. The exact code will be annoted and can be checked against the codes at the bottom of the runway analysis page)

I should also add that you must consider your max. structural weight, and that QNH, bleed, anti-ice usage, and any MEL/CDL items will also need to be taken into account too.

Hope that helps