Once again the man from down under is spot on with his understanding of the use of reverse thrust.

As CoolP described honking hard on the reverse thrust levers will cause grief.



Here is just a look at the engine at idle on a moist day. You can imagine what a good Dyson cleaner these big fan engines can be.
Reverse thrust is not used for certification. Reverse thrust is most effective at high airspeed and most operators require moving towards forward thrust by 80 knots to avoid ingesting exhaust gasses and possible engine compressor stalls.

You all remember this beauty!  





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LOU wrote on Oct 12^th, 2011 at 9:29pm:
CoolP is from "Down Under"?

LOU wrote on Oct 12^th, 2011 at 9:29pm:
That Delta aircraft looks like it wanted to take some "extra" cargo!!!!  

But in all seriousness. OUCH!

Mark

701151 wrote on Oct 13^th, 2011 at 2:27am:
Hmmmm. Interesting way of explaining an incident.

Its a statement, unrealted to the picture, other than the fact the topic in indeed about the C-17 Globemaster III

Markoz wrote on Oct 13^th, 2011 at 1:47am:

Remember, Moth Air has all the routes.   Wanna join?  

We are thinking about Peter being our PR guy.   We just have to make sure there are enough engines and baggage carts available.


The vortex picture is a great one!


Boeing247, that Stratocruiser in the sim has the reverse thrust modelled, but keep in mind that a prop reverses differently than the current hi-bypass jet engines.
They really "flip" the blades to an angle producing thrust in another direction. You can even see that happening on the torque meter as it goes down first and up again as the new direction has established and the engine then has to put power on the shaft again. The sound is very different too.
The whole prop reverse process is way more efficient than the methods used on the jet planes since you get a large amount of the currently produced engine power acting in the now braking direction, except for the exhaust gases.
With the smaller intakes or even very "automotive" ones, the danger of foreign object damage (to the engine itself) also acts in another regime.

The jets don't alter any blade angles (=fixed blades), but more or less try to redirect the airflow they produce. Sir Newton would love that method.
The older ones had those moving buckets, the newer hibypass ones are mostly running with the 'reversed' bypass airflow only while the core still produces 'unreversed' forward thrust.
The amount of the contents differs though, so the bypass part is (by far) the dominant one, in every direction.


Hey, look at the other pictures from Lou, that's the 'Gravel Kit' of the old 737s. I would love to see that modelled in the sim.
Together with a sort of deflector on the front wheel it's really approved to run the jets on the nasty gravel strips, like he says.
Here are some more details. Nice page by the way. http://www.b737.org.uk/unpavedstripkit.htm

The main question will then be: how does this actually help our PR?  
By the way, me no likes full quotes.  

Is it me? I'm never sure if Peter really means what he says.

pj747 said: The reversing thrust on the C-17 goes back through the engine... ???

pj747 then said: Its a statement, unrealted to the picture, other than the fact the topic in indeed about the C-17 Globemaster III

Hummmmmm???  

Peter,

The air from the reverse thrust does not go through the engine. If it did, in any great quantity, it could cause the engine to compressor stall. Most modern large-fan jet engines only reverse (deflect) the fan air, the bulk of the thrust. Smaller engines and older large fan's reversed the fan and the turbine air. This caused too many problems with stalls and unbalanced air flow through the engine. Pilots are instructed to be at idle thrust by 80 knots, so the deflected air is not brought back into the inlet, along with other stuff like dirt or stones that could get sucked into the inlet - not to mention baggage bins!  

---

boeing247 asked: Lou-- did many propliners have reverse thrust?

All of the turboprops alter the blades pitch to control the thrust of the "disk." There is a position called beta where the thrust is about zero. In flight beta can produce a lot of drag since the diameter of the propeller (disk) produces drag equivalent to a solid disk. You can hear the sound produced by the spinning disk as it goes through this phase. The C-130, DHC-6 and most turboprops can use this ability to rapidly alter the blade angle for fine control of the thrust including reverse to back up the plane. Older prop planes also had the ability to change the blade angle and produce reverse thrust. Planes like the Boeing 337 with the P&W-4360 had to be treated with kid gloves when using a lot of reverse so as not to fry the engine or foul the plugs.

Here is a video of a C-17 backing up after landing at an airshow. The C-17 reverse is deflected up and to the side so as to avoid sucking-up stuff off the runway.  In the airline industry doing something like this would cause the CEO to have a heart attack since the chance of engine damage doing this is very high. Wait a minute, CEO don't have a heart so that could not happen!  

C-17 backing up after landing...
http://www.youtube.com/watch?v=T9rdzqOgNrA

A few related videos...
C-17 landing in Afghanistan on a dirt runway. What do you think the descent rate was on touchdown?
http://www.youtube.com/watch?v=diX3x6ffvSA&feature=related
Boeing 737 taxing in snow. You can see the area in front of the engine where stuff is sucked into the inlet.
http://www.youtube.com/watch?v=L1DkUOOfDFk&feature=related
Short video showing the fan blocker doors in operation on a large fan engine.
http://www.youtube.com/watch?v=92ixq3iHFxQ&feature=related

Lou

CoolP wrote on Oct 13^th, 2011 at 3:42pm:

CoolP. I was actually at that air show at Avalon to see it do that. I'll have to dig up the photos my sin took at Avalon 2009.