dogfighter2111
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Reverse Thrust In-Flight On Dash 8

Wed Aug 02, 2006 7:17 am

Hi all,

Well this afternoon i flew EDI-MAN on a BA Connect Dash 8-300. The flight was great, and i loved the final approach. We were being bounced about a lot  Smile

Anyway we were coming in to land and when we were about 3000ft from the ground suddenly the engines sounded as though they were powering up. I thought we were perhaps too slow but as soon as i had heard the power up i was pushed forward out of my seat as though we were slowing down! The way it felt made it obvious that the engeins had been put into reverse and i was unaware that this aircraft was capable of doing this whilst in-flight.

Can anyone just confirm this, even though i think it is obvious i still have that feeling in the back of my mind that it may have been something else.

Thanks
Mike
 
2H4
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RE: Reverse Thrust In-Flight On Dash 8

Wed Aug 02, 2006 7:42 am



I think, more likely, the push forward was created by the increased drag of the flaps being lowered. The higher power setting would have been selected to compensate (partially, at least) for the increased drag from the flaps. That's my guess, anyway...




2H4


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Starlionblue
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RE: Reverse Thrust In-Flight On Dash 8

Wed Aug 02, 2006 8:08 am

Quoting 2H4 (Reply 1):
I think, more likely, the push forward was created by the increased drag of the flaps being lowered. The higher power setting would have been selected to compensate (partially, at least) for the increased drag from the flaps. That's my guess, anyway...

Having been self loading cargo on the Dash-8 a lot, I would say this increase in power is indeed very common, and comes at flap lowering.


After touchdown, the props do reverse.
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Skookum
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RE: Reverse Thrust In-Flight On Dash 8

Wed Aug 02, 2006 9:15 am

The changing of the prop pitch could also create similar sounds to a power increase, and the resultant drag of the flat pitch of the blade is usually felt in large turboprops.
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LimaFoxTango
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RE: Reverse Thrust In-Flight On Dash 8

Wed Aug 02, 2006 9:50 am

Actually, what you felt was the condition levers or props being moved from the cruise position of 900 RPM to the MAX setting of 1200 RPM. The propellers are moved to a position where they're basically flat against the oncoming air which adds quite a bit of drag and thus slows the aircraft down. Placing the aircraft in reverse while inflight is prohibited. The warning sticker in the photo below to the left of the FO's airspeed indicator reads "Positioning of the Power Levers below the flight idle stop during flight prohibited. Such positioning may lead to loss of aircraft control......." you get the idea.


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Photo © Stefan Zahn

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KELPkid
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RE: Reverse Thrust In-Flight On Dash 8

Wed Aug 02, 2006 9:58 am

You would have known if the props were in beta. Propellers in beta make a very distinct, low frequency "growling" sound...(for lack of a better description). It almost sounds like a C-130 taxiing around on the ground  Big grin
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EMBQA
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RE: Reverse Thrust In-Flight On Dash 8

Wed Aug 02, 2006 11:50 am

Quoting Dogfighter2111 (Thread starter):
The way it felt made it obvious that the engeins had been put into reverse and i was unaware that this aircraft was capable of doing this whilst in-flight.

No Turboprop that I know of can go into reverse in flight. VERY-VERY BAD things happen if they do. Most all aircraft that I know of have a Beta Stop to prevent the crew from pulling the power levers too far back when in flight.
"It's not the size of the dog in the fight, but the size of the fight in the dog"
 
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HAWK21M
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RE: Reverse Thrust In-Flight On Dash 8

Wed Aug 02, 2006 1:23 pm

Shouldn't the Reverse Pitch be Air-Grd Sense Related.
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avt007
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RE: Reverse Thrust In-Flight On Dash 8

Wed Aug 02, 2006 1:55 pm

The reverse in the Dash8 can be selected in flight, but it is prohibited, and there is a screamingly loud warning horn that goes off if it is accidently done. LimaFoxTango has it right, the noise and deceleration is the rpm being increased in preparation for a possible go around, also the reverse is more effective on the ground with the condition levers at max rpm.
 
2H4
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RE: Reverse Thrust In-Flight On Dash 8

Wed Aug 02, 2006 2:20 pm




Quoting EMBQA (Reply 6):
No Turboprop that I know of can go into reverse in flight.

I know of only one:





Powerplant - Pratt & Whitney PT6A-25C
Horsepower - 750
Propeller - Hartzell 3 blade composite, 100� diameter
Wingspan - 24 feet
Length - 22 feet, 4 inches
Height - 8 feet, 9 inches
Wing Area - 100 square feet
Seats - 1
Empty Weight - 1,600 pounds
Fuel Capacity - 150 gallons / Jet-A
G Limits - 12 positive / 12 negative
Take-off Distance - 200 feet @ performance weight
Landing Distance - 800 feet (using reverse thrust)
Max Climb - 10,000 fpm @ 120 KIAS
Cruise Climb - 4,500 fpm @ 215 KIAS
Service Ceiling - 30,000+ feet
Fuel Consumption - 45 gph @ cruise power
Range - 800 nm (VFR reserves)
Endurance - 3 hours (VFR reserves)
Vne (never exceed) - 300 KIAS
Vs1 (stall) - 65 KIAS
Vref (approach) - 80 KIAS
Top Speed @ 3,000 feet - 260 KIAS (300 mph)
75% Power @ 3,000 feet - 230 KIAS
Sustainable Vertical Speed - 60 KIAS, 5,000 fpm, straight up!
Exhilaration Factor - "10"




2H4


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Inbound
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RE: Reverse Thrust In-Flight On Dash 8

Wed Aug 02, 2006 2:33 pm

yes that's right, that sound you heard was the condition levers being moved from either 900rpm or 1050rpm to 1200 for landing.

you may also hear it when some hotshots are screaming around to base turn at about 200KIAS and need to create some quick drag to get down to gear and flap extension speeds :p

LimaFoxTango, how are things in antigua tonight? A bit wet??
Caribbean Star has left a few planes in Piarco tonight due to the storm passing thru antigua.
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LimaFoxTango
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RE: Reverse Thrust In-Flight On Dash 8

Thu Aug 03, 2006 2:21 am

Quoting Inbound (Reply 10):
you may also hear it when some hotshots are screaming around to base turn at about 200KIAS and need to create some quick drag to get down to gear and flap extension speeds

I know that one!!! Especially accepting the visual overhead TRI at 4100'.

Quoting Inbound (Reply 10):
LimaFoxTango, how are things in antigua tonight? A bit wet??
Caribbean Star has left a few planes in Piarco tonight due to the storm passing thru antigua.

It was pretty quiet. No wind and hardly any rain just like any other evening.
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vikkyvik
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RE: Reverse Thrust In-Flight On Dash 8

Thu Aug 03, 2006 2:53 am

Quoting 2H4 (Reply 9):
I know of only one:

Christ, that is some serious performance!

In going from 900 up to 1200 RPM and changing the pitch to create more drag (is that coarse pitch or the other one?), is this because in a go-around situation, it is much faster to change the pitch back (thereby quickly increasing thrust) than it is to spool the engines up?

Thanks.

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T prop
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RE: Reverse Thrust In-Flight On Dash 8

Thu Aug 03, 2006 6:21 am

Interesting that the Turbo Raven above is in this thread. It crashed at an airshow oct 99 when the pilot was using reverse inflight and was atempting to switch back to forward thrust at about 800 feet. The pilot says that when he wanted to come out of reverse and pushed the power lever up there was no response from the engine and he continued to sink till he crashed.

BTW, on the Dash 8 reverse is in the beta range. Part of the beta range is available inflight, not reverse though.

T prop.
 
bri2k1
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RE: Reverse Thrust In-Flight On Dash 8

Thu Aug 03, 2006 6:42 am

Quoting Vikkyvik (Reply 12):
it is much faster to change the pitch back (thereby quickly increasing thrust) than it is to spool the engines up?

Power is still set with the thrust levers. The condition levers control the propellor RPM which is only indirectly related to power. The faster the engine turns, the more power it produces. By setting a fine pitch, the blades take a smaller bite of air, and can spin faster. This allows the engine to turn faster, which produces more power. In cruise flight, less power is needed, and by turning the engines slower, less fuel is consumed, so a more coarse pitch can be selected.

It sounds like it would be possible to operate at a coarse propellor setting with a high thrust setting, but in practice this is damaging to the engines.
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N231YE
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RE: Reverse Thrust In-Flight On Dash 8

Thu Aug 03, 2006 9:06 am

Quoting 2H4 (Reply 1):
I think, more likely, the push forward was created by the increased drag of the flaps being lowered. The higher power setting would have been selected to compensate (partially, at least) for the increased drag from the flaps. That's my guess, anyway...

I know the SAAB 340 (SF340) has a similar occurance; when the landing gear is lowered, I always hear a sudden change in the pitch of the propellers, as if they are throttling up (engines)/ changing the prop's pitch slighly to compensate for the increased drag of the extended landing gear.
 
dogfighter2111
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RE: Reverse Thrust In-Flight On Dash 8

Thu Aug 03, 2006 5:53 pm

Hiya all,

Thank you all so much. I never even thought that it could be the props being moved although i was wondering about them moving in-flight whilst i was on the ground in EDI.

Well i am just going away now to catch my return flight.

Thanks
Mike
 
ajd1992
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RE: Reverse Thrust In-Flight On Dash 8

Fri Aug 04, 2006 10:51 pm

If they had engaged reverse pitch inflight, you may notice a wing falling, with you in pursuit Big grin Think of the Lauda 767 over Thailand.
 
dogfighter2111
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RE: Reverse Thrust In-Flight On Dash 8

Fri Aug 04, 2006 11:06 pm

Quoting Ajd1992 (Reply 17):

Yes, i understand that but every aircraft is different and every aircraft has it's won capabilities.

Obviously from that experiance a B767 cannot use Reverse thrust in-flight (That was only one side remember, which also never helped the situation) but the Trident was able to do so.  Smile

Thanks
Mike
 
bri2k1
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RE: Reverse Thrust In-Flight On Dash 8

Fri Aug 04, 2006 11:17 pm

I believe the C-17 Globemaster can use at least idle reverse on at least the two inboard engines (and possibly more) in flight for incredible descent performance. It shares engines (under a different designation) with the P&W-powered 757s, so it seems in-flight reversing capability is really a function of airframe design moreso than of the engine. The C-17 also has a unique reverser design where most of the air is deflected straight ahead or upwards to minimize FOD, which allows it to safely powerback even with wing-mounted engines.
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Starlionblue
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RE: Reverse Thrust In-Flight On Dash 8

Sat Aug 05, 2006 12:01 am

Quoting Bri2k1 (Reply 19):
i2k1 From United States, joined Dec 2004, 681 posts, RR: 1
Reply 19, posted Fri Aug 4 2006 16:17:42 UTC+2 and read 7 times:

I believe the C-17 Globemaster can use at least idle reverse on at least the two inboard engines (and possibly more) in flight for incredible descent performance. It shares engines (under a different designation) with the P&W-powered 757s, so it seems in-flight reversing capability is really a function of airframe design moreso than of the engine. T

Indeed. Also several older jets have had idle reverse in flight capability. For example the DC-8. And I'm pretty sure I remember postings from a 747 captain who left the boards a while a go about idle reverse on the 747 for the purpose of emergency descent. Apparently the noise and vibrations are something else.
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meister808
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RE: Reverse Thrust In-Flight On Dash 8

Sun Aug 06, 2006 1:30 am

Quoting Bri2k1 (Reply 14):
Power is still set with the thrust levers. The condition levers control the propellor RPM which is only indirectly related to power. The faster the engine turns, the more power it produces. By setting a fine pitch, the blades take a smaller bite of air, and can spin faster. This allows the engine to turn faster, which produces more power. In cruise flight, less power is needed, and by turning the engines slower, less fuel is consumed, so a more coarse pitch can be selected.

It sounds like it would be possible to operate at a coarse propellor setting with a high thrust setting, but in practice this is damaging to the engines.

You've got the right idea here, and I know what you mean, but I'm going to clarify a little bit for those people out there who don't know how constant-speed propellers work.

The condition levers control RPM. The power levers control torque. When the RPM is pulled back, the propellers will move to a higher pitch(coarse) so that the same thrust can be produced with less revolutions of the propeller (the prop needs to take a bigger bite out of the air, since it is moving slower). In addition, the high pitch condition produces less drag, so the airplane can go faster with less fuel burn.

What really changes blade pitch is the power lever. Given a constant RPM, an increase in torque will increase pitch (coarse) so that more thrust will be produced. A decrease in torque will decrease pitch (fine) so that less thrust will be produced.

The reason high RPM is selected for takeoff and landing is because, at lower RPMs, the propeller may hit maximum pitch somewhere short of maximum torque, so there will be engine power that is unused (at maximum torque)because the prop can't take any bigger bite out of the air. By increasing RPM to maximum, you ensure that there is adequate blade pitch to use all torque available when the power lever is moved fully forward.

You are also correct in saying that, even if you don't run out of pitch, it is still bad to operate at high torque with the RPM decreased, as it strains the engine components. It would be akin to accelerating your manual-transmission car from 5 to 20 mph in 5th gear with your foot on the floor. It works, but common sense dictates that it will be better on the vehicle (and faster) to match engine RPM with tire RPM slightly better by downshifting a few gears. Every engine and prop combination will have limits published to dictate how much power can be used at certain RPM settings.

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bri2k1
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RE: Reverse Thrust In-Flight On Dash 8

Sun Aug 06, 2006 6:58 am

Quoting Meister808 (Reply 21):
What really changes blade pitch is the power lever. Given a constant RPM, an increase in torque will increase pitch (coarse) so that more thrust will be produced. A decrease in torque will decrease pitch (fine) so that less thrust will be produced.

The reason high RPM is selected for takeoff and landing is because, at lower RPMs, the propeller may hit maximum pitch somewhere short of maximum torque, so there will be engine power that is unused (at maximum torque)because the prop can't take any bigger bite out of the air. By increasing RPM to maximum, you ensure that there is adequate blade pitch to use all torque available when the power lever is moved fully forward.

...

It would be akin to accelerating your manual-transmission car from 5 to 20 mph in 5th gear with your foot on the floor. It works, but common sense dictates that it will be better on the vehicle (and faster) to match engine RPM with tire RPM slightly better by downshifting a few gears.

Good explanations -- better than mine  Smile
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3DPlanes
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RE: Reverse Thrust In-Flight On Dash 8

Sun Aug 06, 2006 9:31 am

Quoting Bri2k1 (Reply 19):
The C-17 also has a unique reverser design where most of the air is deflected straight ahead or upwards to minimize FOD, which allows it to safely powerback even with wing-mounted engines.

They also reverse the core discharge, rather than just the bypass air... Do any of the commercial engines do that?
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Starlionblue
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RE: Reverse Thrust In-Flight On Dash 8

Sun Aug 06, 2006 9:36 am

Quoting 3DPlanes (Reply 23):
Quoting Bri2k1 (Reply 19):
The C-17 also has a unique reverser design where most of the air is deflected straight ahead or upwards to minimize FOD, which allows it to safely powerback even with wing-mounted engines.

They also reverse the core discharge, rather than just the bypass air... Do any of the commercial engines do that?

Not the newer ones in general. Most of the air is in the bypass duct anyway. On older engines, it is pretty common. The Jurassic 737s have core and bypass reverse, for example.

[Edited 2006-08-06 02:36:43]
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LPLAspotter
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RE: Reverse Thrust In-Flight On Dash 8

Mon Aug 07, 2006 1:13 am

Quoting Bri2k1 (Reply 19):
I believe the C-17 Globemaster can use at least idle reverse on at least the two inboard engines (and possibly more) in flight for incredible descent performance. It shares engines (under a different designation) with the P&W-powered 757s, so it seems in-flight reversing capability is really a function of airframe design moreso than of the engine. The C-17 also has a unique reverser design where most of the air is deflected straight ahead or upwards to minimize FOD, which allows it to safely powerback even with wing-mounted engines.

Absolutely correct my friend, and here's the video to prove it:
http://flightlevel350.com/Aircraft_B..._Untitled_Aviation_Video-5025.html

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Av8trxx
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RE: Reverse Thrust In-Flight On Dash 8

Wed May 09, 2007 3:02 am

Quoting N231YE (Reply 15):
I know the SAAB 340 (SF340) has a similar occurance; when the landing gear is lowered, I always hear a sudden change in the pitch of the propellers, as if they are throttling up (engines)/ changing the prop's pitch slighly to compensate for the increased drag of the extended landing gear.

The sound change from the props has nothing to do with compensation for the increased drag from the gear. It just happens that the flow that goes with the "gear down" command is to bring the CLs to max. That is why you hear the sound of the props going to fine pitch at the time the gear is lowered.
 
N231YE
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RE: Reverse Thrust In-Flight On Dash 8

Wed May 09, 2007 3:52 am

Quoting Av8trxx (Reply 26):

Having never flown in an aircraft with constant-speed propellers until recently, I noticed one of the items on the checklist (at least for an PA-28 & PA-44) is to adjust for maximum RPMs just before landing. The purpose: the propeller(s) are ready for best climb should an aborted landing occur. Now that I think about it, this may be an automatic thing in the SF340, that when the gear goes down, the RPMs increase.
 
Fly2HMO
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RE: Reverse Thrust In-Flight On Dash 8

Wed May 09, 2007 5:05 am

Quoting Starlionblue (Reply 24):
The Jurassic 737s have core and bypass reverse, for example.

And for that matter all planes with JT8Ds.
 
KELPkid
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RE: Reverse Thrust In-Flight On Dash 8

Wed May 09, 2007 5:45 am

Quoting N231YE (Reply 27):
I noticed one of the items on the checklist (at least for an PA-28 & PA-44) is to adjust for maximum RPMs just before landing.

My first complex/high performance landing (I took care of both signoffs at once) with an instructor, I neglected the "P" in GUMP. Well, after flaring in the landing (it was a 1962 Cessna 210B), the prop promptly came to a stop  Wow! It was embarrasing, to say the least. I held up all the traffic at 5T6 as my instructor taught me how to do a hot start with a Continental IO-470 on the runway...never made that mistake again  Wink
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meister808
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RE: Reverse Thrust In-Flight On Dash 8

Wed May 09, 2007 10:32 am

Quoting N231YE (Reply 27):
this may be an automatic thing in the SF340, that when the gear goes down, the RPMs increase.

Doubtful - its a purely mechanical system, so unless the guys at Saab tied the landing gear hydraulics into the prop control cables somehow (I can think of no less than 5 reasons right now why thats a terrible idea, too), its pilot controlled. You have to remember, however, that an item on a checklist or profile for an aircraft flown by a trained and standardized crew may as well be automatic - it will happen at the same time, every time, hence the term standardization.

Quoting KELPkid (Reply 29):
hot start with a Continental IO-470

Ouch - that could take a while  Wink

-Meister
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EMBQA
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RE: Reverse Thrust In-Flight On Dash 8

Wed May 09, 2007 10:59 am

Quoting N231YE (Reply 27):
Now that I think about it, this may be an automatic thing in the SF340, that when the gear goes down, the RPMs increase.

Nope... landing check list items. 1) Gear Down.... 2) Props to max.
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N231YE
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RE: Reverse Thrust In-Flight On Dash 8

Wed May 09, 2007 11:15 am

Quoting EMBQA (Reply 31):
Nope... landing check list items. 1) Gear Down.... 2) Props to max.

So that makes sense. On landing, the pilots put the gear down, then they put the props to fine pitch (high RPMs).

The main reason I speculated that the gear->props was automatic is that the two events occurred nearly simultaneously, and I wasn't sure if the SF340 had FADEC (some of the new light GA aircraft have just a throttle; FADEC controls prop and mixture).
 
ThirtyEcho
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RE: Reverse Thrust In-Flight On Dash 8

Wed May 09, 2007 4:32 pm

i was pushed forward out of my seat

Next time, Cappy, pay attention to the seat belt sign and announcement.

The DC-8 could use reverse thrust inflight on the two inboard engines.
 
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Jetlagged
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RE: Reverse Thrust In-Flight On Dash 8

Wed May 09, 2007 7:54 pm

The Trident could also use in flight thrust reverse as a means to make rapid descents. It was possible to select reverse in flight on the 727, but I don't think it was an approved procedure.

Quoting Starlionblue (Reply 20):
And I'm pretty sure I remember postings from a 747 captain who left the boards a while a go about idle reverse on the 747 for the purpose of emergency descent. Apparently the noise and vibrations are something else.

I doubt that. Thrust reverse is interlocked out in flight on the 747. Maybe it used to be possible but the design was changed in the early days? Perhaps he recalled a sim exercise (it's usually available as a malfunction as inadvertent (i.e. unselected) reverse thrust in flight is on the abnormal checklist).

Quoting Starlionblue (Reply 24):
The Jurassic 737s have core and bypass reverse, for example.

The JT8D has a mixed exhaust airflow so naturally all of it is reversed.  Smile The same applies to the RR Spey for example. Older JT9Ds had core reversers but they were soon removed because they were simply not worth the extra weight involved. The JT3D had separate fan and core reverse. In that case it would probably have been the fan reverser which had little to contribute.
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Starlionblue
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RE: Reverse Thrust In-Flight On Dash 8

Wed May 09, 2007 8:54 pm

Quoting Jetlagged (Reply 34):

Quoting Starlionblue (Reply 20):
And I'm pretty sure I remember postings from a 747 captain who left the boards a while a go about idle reverse on the 747 for the purpose of emergency descent. Apparently the noise and vibrations are something else.

I doubt that. Thrust reverse is interlocked out in flight on the 747. Maybe it used to be possible but the design was changed in the early days? Perhaps he recalled a sim exercise (it's usually available as a malfunction as inadvertent (i.e. unselected) reverse thrust in flight is on the abnormal checklist).

Well, it was a long time ago and my memory may be hazy. Perhaps Captain Squares can set the record straight.
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N231YE
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RE: Reverse Thrust In-Flight On Dash 8

Wed May 09, 2007 10:40 pm

Quoting Jetlagged (Reply 34):
Older JT9Ds had core reversers but they were soon removed because they were simply not worth the extra weight involved.

Just to add, some of the early DC-10s with the CF6's had core reversers, but those were removed as well.

Note the "paddle" in the core flow of engine #2:

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Click here for bigger photo!

Photo © Frank C. Duarte Jr.



The same aircraft, nearly 2 decades later, and missing the "paddles:"

View Large View Medium
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Photo © Frank C. Duarte Jr.

 
access-air
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RE: Reverse Thrust In-Flight On Dash 8

Thu May 10, 2007 12:25 am

Quoting LimaFoxTango (Reply 4):
Actually, what you felt was the condition levers or props being moved from the cruise position of 900 RPM to the MAX setting of 1200 RPM. The propellers are moved to a position where they're basically flat against the oncoming air which adds quite a bit of drag and thus slows the aircraft down.

This is exactly what is going on.....The power levers are not moved..only the propeller pitch levers taking the props out of their Wide open pitch to a more modest pitch. If you have ever flown on the ATR-42/72 or a SAAB 340 this same precedure is performed.....Its actually the opposite on take off.....When you take off, the props pitch increases for take off but after lift off, after the aiurcraft has established its climb you can always hear what sounds like a the pilot cutting back on the power...That is not so...he is just increasing the angle of the props to take that bigger bite of the air and that action slows the engine's RPMs.

Access-Air
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flyboy80
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RE: Reverse Thrust In-Flight On Dash 8

Thu May 10, 2007 12:15 pm

When I used to work dash 8s we would just come screaming in (apply that definition as you well with this particular aircraft) to some airports, guys up front would drop gear, put in some flaps, and you would hear them change the props all within seconds of each other...we would slow down so quick sometimes I thought we were turning into an osprey!!!
 
71Zulu
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RE: Reverse Thrust In-Flight On Dash 8

Fri May 11, 2007 6:21 am

Quoting EMBQA (Reply 6):
No Turboprop that I know of can go into reverse in flight. VERY-VERY BAD things happen if they do. Most all aircraft that I know of have a Beta Stop to prevent the crew from pulling the power levers too far back when in flight.

Very bad things indeed

http://www.airdisaster.com/reports/ntsb/AAR88-08.pdf
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RE: Reverse Thrust In-Flight On Dash 8

Fri May 11, 2007 7:03 pm

Quoting Access-Air (Reply 37):
This is exactly what is going on.....The power levers are not moved..only the propeller pitch levers taking the props out of their Wide open pitch to a more modest pitch. If you have ever flown on the ATR-42/72 or a SAAB 340 this same precedure is performed.....Its actually the opposite on take off.....When you take off, the props pitch increases for take off but after lift off, after the aiurcraft has established its climb you can always hear what sounds like a the pilot cutting back on the power...That is not so...he is just increasing the angle of the props to take that bigger bite of the air and that action slows the engine's RPMs.

Most of the time, we're pushing the power levers forward at the same time the non-flying pilot is pushing the condition levers forward. Maintains a relatively constant torque setting as the props go flat. Unless of course you're using the props to slow down. Then I still add power as the props come up, then gradually take it back out to keep the pax from eating the seats in front of them.
 
cdekoe
Posts: 53
Joined: Thu Nov 30, 2006 1:14 am

RE: Reverse Thrust In-Flight On Dash 8

Thu Jun 07, 2007 3:03 am

Quoting DashTrash (Reply 40):
Most of the time, we're pushing the power levers forward at the same time the non-flying pilot is pushing the condition levers forward. Maintains a relatively constant torque setting as the props go flat. Unless of course you're using the props to slow down. Then I still add power as the props come up, then gradually take it back out to keep the pax from eating the seats in front of them.

Can anybody here tell me what the engine RPMs are during the cruise, descend, approach and landing phase of the Dash 8 flight profile?

Thanks!
We can't solve problems by using the same kind of thinking we used when we created them.
 
LimaFoxTango
Posts: 795
Joined: Wed Jun 16, 2004 11:33 pm

RE: Reverse Thrust In-Flight On Dash 8

Thu Jun 07, 2007 5:25 am

Quoting Cdekoe (Reply 41):
Can anybody here tell me what the engine RPMs are during the cruise, descend, approach and landing phase of the Dash 8 flight profile?

Normally 1200RPM for take off, 1050RPM for climb, 900RPM for cruise, descent and approach and 1200RPM for landing.
You are said to be a good pilot when your take-off's equal your landings.
 
cdekoe
Posts: 53
Joined: Thu Nov 30, 2006 1:14 am

RE: Reverse Thrust In-Flight On Dash 8

Thu Jun 07, 2007 5:38 am

Quoting LimaFoxTango (Reply 42):
Normally 1200RPM for take off, 1050RPM for climb, 900RPM for cruise, descent and approach and 1200RPM for landing.

Thanks for the quick reply!

Would you happen to know related core engine speeds? I'm looking for the variation in accessory gearbox drive - AC generator RPM.

Thanks again.
We can't solve problems by using the same kind of thinking we used when we created them.
 
CF188A
Posts: 680
Joined: Sun May 07, 2006 12:27 am

RE: Reverse Thrust In-Flight On Dash 8

Thu Jun 07, 2007 11:27 am

Someone correct me if I am wrong, but the Buffalo can and does engage reverse thrust before they touch down. I witnessed it several times.
Dream as if you'll live forever. Live as if you'll die tomorrow~ RIP ... LJFM
 
WrenchBender
Posts: 1662
Joined: Wed Feb 04, 2004 5:59 am

RE: Reverse Thrust In-Flight On Dash 8

Thu Jun 07, 2007 11:56 am

Quoting CF188A (Reply 44):
Someone correct me if I am wrong, but the Buffalo can and does engage reverse thrust

It can be selected but requires weight on wheels switch to be made to actually activate. Like most DHC products 'Prop discing' is used as a speed brake. It is a low pitch setting for the prop, not a negative pitch setting.

WrenchBender
Silly Pilot, Tricks are for kids.......
 
DashTrash
Posts: 1266
Joined: Mon Aug 21, 2006 8:44 am

RE: Reverse Thrust In-Flight On Dash 8

Tue Jun 12, 2007 1:56 pm

"Discing" is the same as beta in the Dash 8. You can't do it in flight. The beta lockout system prevents it.

If you lift the triggers to bring the power levers back, you get a horrible sounding alarm. If you pull the levers past the flight idle gate, the engines respond in the opposite manner, adding torque. When you bring them back out of disc, Both ECU's will "lock out", and maintenance must reset them. That is the tattle tale feature of the system.

Without the beta lockout system, it would be possible to go into disc in flight, but it is unwise to do so.

Don't know the actual engine speeds for the Dash. We've got two types of engines in our fleet. The PW120A on the -100s and the PW123 on the -300s. They both turn at different speeds and use percentage to measure the RPM.

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