View Full Version : AirWrench & Zero Lift Drag

January 7th, 2009, 08:32
Mr. Beckwith,

I am working on FDE for a Supermarine Seagull / Walrus, and
am seeing very large drag values in both Airwrench and the Flight Dynamics Workbook.

Would you kindly comment / teach about the Zero Lift Drag numbers
as indicated by the Pics Below, and how they relate to the specified Horsepower and other pertinent settings such as prop efficiencies ?

Thank you for your consideration,






January 7th, 2009, 13:48
The Mach drag figure seems to be off the wall.... Also note that it would appear that the terminal velocity figure you have is probably OK for a dive bomber with the air brakes extended. Is it possible the overall drag is being calculated with dive brakes extended?

You are just using Airwrench in demo mode? You could fix this in Airwrench by entering new figures in the speeds on the first page, and a few other things.

Jerry could of course provide a more complete answer, a little hard to judge without seeing the workbook entries.

Good luck: T.

January 7th, 2009, 14:10
Yes, the drag values you're seeing in the tools are large, but not unreasonable for the aircraft type you're modelling.

The estimated drag range that AirWrench displays is based on the 'Aircraft Type' selected on the Tuning tab, which you have set to 'General Aviation'. That's a perfectly good choice for this aircraft, and I wouldn't change it. But the expected drag range was derived from more modern general aviation aircraft types from manufacturers like Beech, Cessna, Piper, Mooney, etc.

January 7th, 2009, 22:32
Thank you for your replies Fliger747 & Sparks.

That 38 - 74 range makes much more sense in that context (being derived from typical GA examples).

Fliger747 - thank you for your input - I have read pilots report that state the Walrus' terminal velocity was not much greater than its level flight Vmax - that is somewhat confirmed by this resultant dive velocity then.

Thank you for the tools Sparks, they are great - esp. the FDWB, I am getting quite fond of tinkering with FDE's now.

Airwrench makes you want to change all the default aircraft's FDE's too LOL - I hate to see the balance sheet not reflecting a logical layout, and most commonly tires that are way too big !

Cool toys these are !:applause:

Keep well,


PS. I miss the tutorial by Sparks that SOH had before the crash (p47 i think ?)