Jump to content
Sign in to follow this  
PilotNL

Climb performance calculation

Recommended Posts

Hello all! I have a question about the climb performance calculation with the 737. Last week I made 2 different flights, one departing from LOWI and one from LFMN. Both require a climb gradient, LOWI RATT2J departure has a required climb gradient of 4,7% due to a cumulus granitus in the takeoff sector :) It is located at 17 NM after DER (18,2NM after brake release) and 4700ft-AAL (6700AMSL) For LOWI I used the PMDG FCOM1 PD.30.9 (page 366) Takeoff obstacle limit weight. This table only counts for obstacles up to 300m and 9km from brake release so I am not sure this is the correct table to use, but because I cannot find any other, I used it be calculating a fictional obstacle of at 6km and that would be 282 meters high. With these figures I went into the tables and find:58.4t reference obstacle limit weightno OAT adjustment required-4.3t pressure altitude adjustment5kt hw correction = +0,4tPacks OFF +0.6t Climb Performance limited weight of: 55.1t This sounds pretty reasonable. In the FMS I typed thrust reduction altitude 4500AGL and acceleration and EO acceleration altitude 7500 (due to a second 3.3% sid part up to 9500) I am pretty sure these figures are based on an engine failure after V1. when I flew the departure with 2 engines on, I had a way better climb performance. Now to France, LFMN has a minimum climb gradient of 7% (!) up to FL100 for ATC reasons. If I use the same way of calculating I end up with a 280m obstacle at 4km.this would give me: 48.6t reference obstacle limit weightno OAT adjustment requiredno pressure altitude adjustmentno hw correctionPacks OFF +0.6t Climb Performance limited weight of: 49.2t But the major difference with Innsbruck is: In Nice, there is no actual obstacle. If I have an engine failure after v1, I would accelerate over the Mediterranean sea, inform ATC request vectors for landing. The 49.2 t restriction is too limiting. The climb limit weight in table PD.30.2 (page 360) is based on the normal 3.3% climb gradient so I cannot use it. On page PD.32.6 I found another climb gradient table, but it is only for flaps 15 and used for GA thrust. For Nice I skipped the climb limiting performance calculation, used no de-rate and no assumed temperature and I made it!But next time I would like to correctly calculate rather then try and hope. Any help would be welcome! :)


vpa118.png

Rico van Dijk

Share this post


Link to post
Share on other sites

Wow why I can't exactly help you with your issue I'd certainly like to get an answer as well. Your method sounds reasonable even if it's "abusing" the chart a little bit. I see no other chart that deals with gradients except for the one with go arounds. sig.gif

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

  • Tom Allensworth,
    Founder of AVSIM Online


  • Flight Simulation's Premier Resource!

    AVSIM is a free service to the flight simulation community. AVSIM is staffed completely by volunteers and all funds donated to AVSIM go directly back to supporting the community. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. Thank you for your support!

    Click here for more information and to see all donations year to date.
×
×
  • Create New...