DC-3 decision speed

Richard

Richard

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It is interesting that on the DC-3 varient I'm looking at, V1, V2, Vx, and Vxse are the same airspeed.

My question is, how would this alter the pilot's decision when an engine fails at V1?

Are there other planes that have this commonality in these Vspeeds?
 
That IS interesting. ;)

For comparison, since Vxse is the speed for climbout on the accelerate-go charts, some of the early King Air 90's actually called it a "decision speed" in the AFM (although "V1" is never used), and also use it as the abort speed for accelerate-stop charts. But it doesn't take a whole lot of chart manipulation to discover that there are a LOT of conditions of weight, altitude, and temperature where continuing the takeoff from an engine failure at Vxse would be a very unwise choice, and at some point Beech took the "decision speed" terminology out of the AFM's.

I'd almost bet the DC-3's have a similar situation, and using it as a decision speed the same way we do in Part 25 airplanes might not be the best idea.

Fly safe!

David
 
Thank you for your response.

So, if "V1" is removed, and it is no longer called "decision speed", what have you? I mean, I don't care what you call it, more important is what speed do you call for abort and what speed do you continue with takeoff?

BTW: the Vspeed on the DC-3 with Wright 1830s is 84 KIAS.

http://www.theaviatornetwork.com/download.htm

See, Oral Exam Powerpoint Study Guide

Yeah, I'm getting excited again to get my PIC DC-3 type rating.
 
MauleSkinner said:
That IS interesting. ;)
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BTW: what the heck does that mean? Am I missing something? Have I forgotten something?

(I'm just a comm rated pilot with ME gotten in a spam can ME trainer. I don't know shiist about ME beyond Seneca/Seminhole.)
 
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What I remember from my DC-3 dual is that the VSpeed was only derived for one aircraft configuration and one atmospheric configuration.

What I've recall from part 25 jet performance tables is a set of tables where you calculate effective runway length based on the runway, the wind, and the atmosphere, and then read off the Vspeeds based on aircraft weight.

In the DC-3 (certified much earlier), you may have a table more like we see in the Seminole, where the speed is preset, and the takeoff distance varies with weight, and wind and atmosphere.

You can reach the same (do I want to use this runway?) conclusion either way - in the jets the tables make it a little more obvious (to me anyway) - you either get a set of vspeeds for the runway (and they'll vary based on effective runway length), or you can't use the runway at all. In the DC-3, you have to compare the available runway length to the takeoff distance in the table and decide if you wish to use the runway.

Disclaimer - I just woke up and haven't had coffee, eaten breakfast, or cracked a book. This reduces the PAA (Probable Answer Accuracy) by as much as 45%.
 
Ken Ibold said:
A J-3 cub on floats takes off at 60 mph, climbs at 60, cruiuses at 60 and descends at 60. In that thing, it's really "on" and "off".
Click to expand...

IIRC Stinsons and Stearmans are flown similarly albeit using a slightly different single speed.
 
Ken Ibold said:
A J-3 cub on floats takes off at 60 mph, climbs at 60, cruiuses at 60 and descends at 60. In that thing, it's really "on" and "off".
Click to expand...
When I asked, "these Vspeeds" it was in reference to ME aircraft...V1, V2, Vx, and Vxse.
 
Richard said:
Thank you for your response.

So, if "V1" is removed, and it is no longer called "decision speed", what have you? I mean, I don't care what you call it, more important is what speed do you call for abort and what speed do you continue with takeoff?

BTW: the Vspeed on the DC-3 with Wright 1830s is 84 KIAS.

http://www.theaviatornetwork.com/download.htm
Click to expand...
Basically, if "V1" is removed and it's no longer called "decision speed", you've got the same criteria for continuing the takeoff that you'd have in a Seminole...You determine a speed or altitude at which you can continue flight while avoiding terrain impacts, and use that as your decision point. Basically, if an engine fails, and you've got time to reconfigure to the flaps up/gear up/prop feathered/cowl flap closed, etc., that's required in order to make your climb performance chart before hitting the ground again, you continue.

In order to properly answer your question, I'd have to find an AFM for a DC-3 and do some research...I'd need to look at performance charts and flight manual procedures to determine whether this is a "bogus V1" or not. The link you provided is basically that particular company's training manuals, which are often oversimplified in my opinion (that's basically the reason for the "That IS interesting ;)" comment). While the airplane appears to be certificated under CAR 4b (not the Part 25 that the training manuals say--very similar, but still not the same), and CAR 4b airplanes DO have V1 and V2 numbers, I'd expect them to move around a little with weight as Tim indicated, particularly on an airplane that has nearly as much useful load and nearly the same MGW as the Hawker I fly (also a CAR 4b airplane, contrary to the Part 25 that all the training manuals I have say it is ;)).

Fly safe!

David
 
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