here's a question!

[murfdawg998]

Does anybody here know the value of D?

 

[Clandestine]

complicated.

 

[murfdawg998]

I understand it's rather complicated, but I was hoping there were some hawker drivers out there who wouldn't mind explaning it to me.

 

[Roadie]

It's been several years since I've flown the Hawker or been to recurrent, so maybe some of the current Hawker drivers can correct me. As I remember, the value of D is the factored equivelent runway distance required that is derived from the charts. The factors are field elevation, slope, temp, wind,weight, etc. and can be worked in reverse (i.e. to find the max weight allowed)

The charts are hard to read, and very British. I only remember using them once or twice for critical ops (short runway/high field elevation situations). Tab data works 99% of the time.

 

[murfdawg998]

Thanks for your help, Roadie...This does seem rather complicated. Sounds a bit like doing calculus with performance charts!

 

[cherokee]

Roadie had it pretty much right. A 'D' value is a theoretical runway length that you figure out by using variables such as wind, gradient, V1/VR ratio. There are other charts you can use to get a runway distance but using 'D' values gives you the most accurate info and is usually used if you are very tight on runway length. As I said you can use the other charts (tab data and simplified charts) most of the time when you're not really tight on distance. The tab data is the easiest to use but does not take into consideration slope, gradient, V1/VR ratio...so if you really needed to use the maximum benefit of such conditions you would use 'D' value charts. In my opinion they are not really that hard to use as long as you understand what you're trying to do. They are just a more complicated form of the charts you've been using since flying the Cessna 152. Of course, you can make it easy and use an Ultra Nav, but that won't get you through initial

 

[unclematty]

value of D' = Rwy length corrected for slope, HW or TW, stopway, and/or clearway.

think of it as a runway that is made longer for a downhill slope, HW, stopway and clearway. OR a runway made shorter for uphill slope, TW, and/or absence of a clearway or stopway.

As others have mentioned, one does not typicaly use Value of D' charts, unless one is trying to take off at the absolute max. weight or is operating at an airport that is not covered by tab data (e.g. KASE).

Do remember tab data only uses a 2.4% gross gradient, based on FAR 25 certification. While a std. IFR departure gradient is 3.3%

PM me with questions.

 

[h25b]

I flew the Hawker 800's for three years and at each recurrent the performance class began with the instructor encouraging everyone who didn't own an ultranav to buy one. That said though, the above posters are right on the money. The Hawker basically has you take whatever runway your flying out of and either figuratively lengthen it or shorten it depending on ambient condition for a given situation... Then you go back in to the charts with your derived "d" value to figure what you need to know...

BUY AN ULTRA-NAV!!!!!

 

[murfdawg998]

Thank you all for your info.....Seems like the UltraNav is the way to go!!!