Beta and Reverse.

[Medivacer]

The Beech 18 thread got me thinking.

First, a real man fly's a bird with an R-985 on it, preferably only one. 2 really isn't needed to prove your manhood.

But all kidding aside.

Someone mentioned that the fitst PT-6 wouldn't go into beta or reverse. Now it's been a few years since ground school, and I don't have any books to read out here, but isn't BETA reverse? As I understand it: 0 thrust is neither Alpha or beta range, but feather, and any negative thrust would be in the beta range or reverse thrust. So beta and reverse are one and the same.

Thinking about it really did keep me up at night, as it's 0200 right now. That or the activity of a major airport in Iraq during the night.
(F-18's, EA6-B's CH-53's and a MV-22's to name a few)

 

[Coool Hand Luke]

Someone mentioned that the fitst PT-6 wouldn't go into beta or reverse. Now it's been a few years since ground school, and I don't have any books to read out here, but isn't BETA reverse? As I understand it: 0 thrust is neither Alpha or beta range, but feather, and any negative thrust would be in the beta range or reverse thrust. So beta and reverse are one and the same.

Thinking about it really did keep me up at night, as it's 0200 right now. That or the activity of a major airport in Iraq during the night.
(F-18's, EA6-B's CH-53's and a MV-22's to name a few)

Not sure about the PT-6 as I have no experience with them but I think all turbo props are the same in this regard. For the Pratt PW118's/Hamilton-Sunstrand props on the EMB-120 Beta range starts at +17.6 deg. blade angle. Obviously reverse woudln't technically occur until -0.1 deg blade angle, and on the EMB-120 goes all way to -15.0 deg.

So what's the word on the street on the MV-22's over there? Not hearing much about them stateside.

 

[Medivacer]

When they first got here people were nervous, no thanks to all the negative press.

Now that reality has set it, people love them. They climb faster than a homesick angel and are pretty much twice as fast as any other chopper we have in the fleet.

Pretty much everything Time magazine printed in October was way off the mark.

For your veiwing pleasure:
http://www.youtube.com/watch?v=8hKTlrKTJhU

 

[great cornholio]

Its been a few years since my BE 1900 days, but if I remember correctly Beta is a negative pitch on the blade and the engine stayed at idle power. Reverse was called something like "beta with power" where the prop blades would go into an even further negative pitch and the engine would start to spool up as well. But like I said its been like 4 years since I've flown the 1900 so I might be totally wrong.

 

[avbug]

You're correct in that beta is everything that isn't the forward, or alpha range. However, in general context, the beta range is typically taken to be a zero thrust range between forward and reverse. Common use differentiates between "just over the gate" when the propeller or power lever controls are just over the gate. Beta is generally taken to be that time when the power lever is moved far enough aft that the fuel control is scheduled to produce increasing power while the propeller is scheduled into a negative angle.

When retarding the power levers to idle in the flight range, you don't control propeller blade angle. The propeller governor does that. In the reverse range, you schedule both power and blade angle with the power levers.

 

[Coool Hand Luke]

When they first got here people were nervous, no thanks to all the negative press.

Now that reality has set it, people love them. They climb faster than a homesick angel and are pretty much twice as fast as any other chopper we have in the fleet.

Pretty much everything Time magazine printed in October was way off the mark.

For your veiwing pleasure:
http://www.youtube.com/watch?v=8hKTlrKTJhU

That's good to hear. Thanks for the video too. Have any been used for dustoff yet?

 

[FreightPup]

In PT-6 powered airplanes, such as the BE-8T or the BE-99, zero forward thrust is achieved on the ground, in the Beta range, by lifting the thrust levers out of the idle gate. This puts the propeller blades in an almost completely flat pitch position with the engine at essentially idle power. The further back you pull the thrust levers from here on out, you are in the Reverse range. The reverse thrust increases, as does the negative blade angle, the more you pull the 'throttles' back into the reverse thrust range. Early PT-6's did not have this gate at all. There was no Beta range, nor Reverse range. The throttles were operated just like a reciprocating engine, whereas idle power was just that, and the blades remained in a slightly forward (low) pitch. Throttle response, was agonizingly slow.

 

[MauleSkinner]

When retarding the power levers to idle in the flight range, you don't control propeller blade angle. The propeller governor does that. In the reverse range, you schedule both power and blade angle with the power levers.

With a little change in terminology, this is basically what I was taught..."alpha" range, which is not a term normally used, is when the propeller governor controls blade angle. "beta" range is when the power lever angle directly controls blade angle.

Generally, in both PT6's and TPE-331's, beta range starts behind the flight idle gate, and goes through reverse.

Fly safe!

David

 

[Fblowjets]

Beta is a ground fine position. Its still positive but between 3 and 11 degrees. Reverse is a negative pitch -5 to something or another.

 

[Hikoushi]

Some aircraft encounter a "flight beta" range with power lever positions ABOVE the flight idle gate. The DHC-8 is an example. The prop blade angle is still positive, but during this brief area just above the flight idle position, the beta metering valve opens, giving direct blade angle control to the power lever. From what I understand, this feature was utilized in the Dash-7 to allow fine glidepath control into the short & confined fields for which the plane was intended, and was carried forward into later models in a less-extreme form.

In this case "Beta range" refers to the range of power lever positions that directly control blade angle through the beta valve, as opposed to the PCU governor automatically varying blade angle to control commanded prop RPM. In the Dash this includes part of the "alpha" range (positive blade angles up to about 18 degrees) as well as negative "ground range" blade angles.