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Topic Author
Posts: 458
Joined: Sun Jun 26, 2005 1:16 pm

### I Need Some Information About The C23 And Navajo

I'm currently doing my homeworks for my flight theory class and I need some information that I'm not able to find anywhere. I'd really appreciate your help.

What I need about the Beechcraft C-23 Sundowner is:

Sweep (25° chord)
Max zero fuel weight
max operating mach

And for the Piper Navajo PA-31-3xx

Sweep (25° chord)
Max operating mach

Ben

thegreatchecko
Posts: 689
Joined: Sat Mar 06, 2004 3:34 pm

### RE: I Need Some Information About The C23 And Navajo

Max operating mach of a Sundowner and Navajo? They definitely don't fly high enough or fast enough for their speeds to be measured in mach.

I wish I could help further, but you are going to have to get the TAS and convert it to mach on the old E6B if you really need those numbers.

You know, I really don't miss these theory type homeworks, they teach you some concepts but sometimes aren't any more useful in the long run than busywork. Have Fun!

Checko

AJ
Posts: 2304
Joined: Wed Nov 03, 1999 3:54 pm

### RE: I Need Some Information About The C23 And Navajo

My PA-31-350 Manual says Vne is 236kcas/kias with a sweep very close to zero!

onetogo
Posts: 286
Joined: Thu Feb 02, 2006 1:40 pm

### RE: I Need Some Information About The C23 And Navajo

Bizarre. Wing sweep back and wing chord are different things.

Even more bizarre!

ballpeeen
Posts: 76
Joined: Mon Aug 22, 2005 8:05 am

### RE: I Need Some Information About The C23 And Navajo

 Quoting Onetogo (Reply 3):Bizarre. Wing sweep back and wing chord are different things.

The question is most likely asking what the measured sweep of the wing is at 25% of MAC (Mean Aerodynamic Chord).
MAC is a useful reference when comparing different wing shapes, and is a common reference in aerodynamics.

I'm pretty sure that the Beech wing is as rectangular as they come, though, so in that case, MAC is the same as measured chord.

I do have to agree that asking for the speed in Mach is kind of weird, though.

Topic Author
Posts: 458
Joined: Sun Jun 26, 2005 1:16 pm

### RE: I Need Some Information About The C23 And Navajo

I know it's weird but my teacher absolutey wanted the speeds in Mach. I have to agree with thegreatchecko on his point, sometime homework aren't usefull at all. And yep I had fun hehe!

Ben

Illini_152
Posts: 959
Joined: Sun Jan 14, 2001 6:00 am

### RE: I Need Some Information About The C23 And Navajo

Than your teacher is a flipping idiot, as neither aircraft goes fast enough or flies high enough to suffer from high-mach aerodynamics, and as such, that number was never published. Let me guess, this is an aviation science class, taught by a CFI who has never flown anything bigger than a Cessna 310? Vne (and Vd) are what piston aircraft are certified with; you cannot just convert the indicated Vne to a mach number, as that will change with temperature and true airspeed.

For example, if your Vne is 170 KIAS at 5000' that would be 182 KTAS and with a TAT of 10C, that would correspond to .270 Mach. Now decrease your TAT to M10C and you're .289 Mach. That same 170 KIAS at 15,000' is 213 true, and .325 Mach at 10C.

None of these would be LIMITS though, as Mmo refers to the limiting mach number; the airplanes never suffer from mach effects to begin with. Now, what would be possible to do would be to chart the aircraft's Vne in indicated airspeed and see how it corresponds to Mach number and True Airspeed.

If your teacher didn't say something like "what is the mach number when at Vne in a Sierra at sea level on a 15C day" you don't have enough information to calculate the answers.

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