Question for Bob Gardner

Bob, in your book "The Complete Advanced Pilot" - Third Edition, in the
section on turbine engines on page 13-6 you state:

"The control quadrant will have three sets of knobs, like any other twin,
but one set will be called 'condition levers'. The throttle and mixture
controls perform their usual functions, while the condition levers are
similar but not identical to prop controls."

Shouldn't that last sentence read: "The throttle and prop controls perform
their usual functions, while the condition levers are similar but not
identical to mixture controls."?

I am trying to get a better understanding of the use of the "condition
levers" and the effects of their settings of "High Idle" and "Low Idle".

Thanks,
Art Varrassi
PP-ASEL

Good question, and I can't give you an answer that applies to all
turboprops. The condition levers have an idle cutoff position, which is
about the only parallel with a mixture control that I can think of. Never
heard of a mixture control with low-idle and high-idle settings. IOW, it is
difficult to make an exact comparison.

This is from a C-90:

Propulsion Systems and Controls
Operated by three sets of controls:

Power Levers: control engine power from idle to take-off power by adjusting
the N1 speed governor in the FCU. Increasing N1 results in increased power.
Propeller Levers: Control the constant speed propellers through the Primary
Governor.
Condition Levers: 3 position lever; CUT-OFF, LOW-IDLE, and HIGH-IDLE.



In any event, almost 100 percent of all turboprop pilots are going to get
formal training (as I did, a long time ago, in a class with astronaut Alan
Shepard) before the insurance company lets them fly. THE COMPLETE
MULTIENGINE PILOT (title chosen by the publisher, not by me) is hardly the
place to look for details on turboprop operation.

I never flew with Garret engines, but I'll bet that there are plenty of
differences between them and PT-6s.



Bob Gardner





"Art Varrassi" wrote in message
news:_zXBd.608139$wV.310377@attbi_s54...

Bob, in your book "The Complete Advanced Pilot" - Third Edition, in the
section on turbine engines on page 13-6 you state:

"The control quadrant will have three sets of knobs, like any other twin,
but one set will be called 'condition levers'. The throttle and mixture
controls perform their usual functions, while the condition levers are
similar but not identical to prop controls."

Shouldn't that last sentence read: "The throttle and prop controls perform
their usual functions, while the condition levers are similar but not
identical to mixture controls."?

I am trying to get a better understanding of the use of the "condition
levers" and the effects of their settings of "High Idle" and "Low Idle".

Thanks,
Art Varrassi
PP-ASEL

Hi,

The condition levers are the analog of the mixture controls. They are
coded the same color (red), and in the same position on the quadrant
(far right) as mixtures, but they actually do not do the same thing as
mixture controls.

A mixture control changes the air-fuel ratio (piston engine). In the
turbine, the condition lever is used to control whether fuel is going
to the engine or not (bottom stop is CUT-OFF). The other two positions
set the idle speed of the engine, i.e. what turbine (N1) speed the
engine will run at when the 'power levers' (those black things that we
call throttles) are pulled back to the idle position. The mixture is
actually controlled automatically by the fuel controller.

So, for example, in a King Air, you have Power Levers, Prop Levers, and
Condition Levers; they look much the same and are in the same positions
as the throttles, prop and mixture controls in a piston twin.

The effect of the condition levers is to either 1) shut off fuel to the
engine (cut-off), or to set the idle governed speed for ground
operations (typically 25% N1), or to set the idle speed for flight
operatons (typically 50% N1). They have these two settings because the
turbines have so much power at flight idle that on the ground you
wouldbe constantly riding the brakes to maintain a safe taxi speed, and
scattering miscellaneous small aircraft in your prop blast as you
maneuvered on the airport. The machine is much easier to manage on the
ground with and idle of 25% N1. However, if we used ground idle in
flight, at idle power the drag on those two huge props would be
excessive, and the airplane would develop a dangerously high sink rate
if the pilot ever pulled back to idle, say on a slightly high approach
on final. Compounding this problem is the long spool-up time the
engine would require if the pilot suddenly decided he wanted power
again after letting the engine spin down to 25% N1 (Remember the Paris
Airshow crash of the Airbus?) So, in flight we keep the condition
levers in the Flight Idle stop, so that if we ever pull the power
levers back to idle on final we won't make one of those big, smoking
holes in the ground just short of the runway.

Right after touchdown it gets a little busy as you come in with the
brakes, pull the power levers up and over their lockouts and back into
the thrust reverse positions; then move back over to the condition
levers and pull them back into ground idle so that once we come out of
reverse we will not have the flight idle thrust fighting the brakes;
but then we have to bring the right hand back over to the power levers
and bring them forward, out of reverse before we get below about 40
KIAS, because at those speeds in reverse the props tend to suck things
up off the runway and get damaged (really expensive) so we put them
forward as we hit 40. While you are doing all of this with your right
hand, your left hand has to be holding the elevator back (ugh) by
itself, your feet have to keep us on the centerline and your toes have
to apply just enough equal braking pressure so that we stop in time,
but not so much that we trigger the anti-lock system and scare all the
passengers.

that's a normal landing... add a slick runway and a stiff crosswind and
you will be just a little more busy...

Regards,

Gene
CFII, MEI, ASC

Excellent! Thanks. So let me see if I have this right; After engine start
the condition levers would be in ground (low) idle through taxi and takeoff
and I would move them to flight (high) idle at cruise. They would stay at
flight idle through descent, approach, and landing and then moved to ground
idle during thrust reversal in preparation for taxi again. Sound ok?

"CFII_ASC" wrote in message
ps.com...
Hi,

The condition levers are the analog of the mixture controls. They are
coded the same color (red), and in the same position on the quadrant
(far right) as mixtures, but they actually do not do the same thing as
mixture controls.

A mixture control changes the air-fuel ratio (piston engine). In the
turbine, the condition lever is used to control whether fuel is going
to the engine or not (bottom stop is CUT-OFF). The other two positions
set the idle speed of the engine, i.e. what turbine (N1) speed the
engine will run at when the 'power levers' (those black things that we
call throttles) are pulled back to the idle position. The mixture is
actually controlled automatically by the fuel controller.

So, for example, in a King Air, you have Power Levers, Prop Levers, and
Condition Levers; they look much the same and are in the same positions
as the throttles, prop and mixture controls in a piston twin.

The effect of the condition levers is to either 1) shut off fuel to the
engine (cut-off), or to set the idle governed speed for ground
operations (typically 25% N1), or to set the idle speed for flight
operatons (typically 50% N1). They have these two settings because the
turbines have so much power at flight idle that on the ground you
wouldbe constantly riding the brakes to maintain a safe taxi speed, and
scattering miscellaneous small aircraft in your prop blast as you
maneuvered on the airport. The machine is much easier to manage on the
ground with and idle of 25% N1. However, if we used ground idle in
flight, at idle power the drag on those two huge props would be
excessive, and the airplane would develop a dangerously high sink rate
if the pilot ever pulled back to idle, say on a slightly high approach
on final. Compounding this problem is the long spool-up time the
engine would require if the pilot suddenly decided he wanted power
again after letting the engine spin down to 25% N1 (Remember the Paris
Airshow crash of the Airbus?) So, in flight we keep the condition
levers in the Flight Idle stop, so that if we ever pull the power
levers back to idle on final we won't make one of those big, smoking
holes in the ground just short of the runway.

Right after touchdown it gets a little busy as you come in with the
brakes, pull the power levers up and over their lockouts and back into
the thrust reverse positions; then move back over to the condition
levers and pull them back into ground idle so that once we come out of
reverse we will not have the flight idle thrust fighting the brakes;
but then we have to bring the right hand back over to the power levers
and bring them forward, out of reverse before we get below about 40
KIAS, because at those speeds in reverse the props tend to suck things
up off the runway and get damaged (really expensive) so we put them
forward as we hit 40. While you are doing all of this with your right
hand, your left hand has to be holding the elevator back (ugh) by
itself, your feet have to keep us on the centerline and your toes have
to apply just enough equal braking pressure so that we stop in time,
but not so much that we trigger the anti-lock system and scare all the
passengers.

that's a normal landing... add a slick runway and a stiff crosswind and
you will be just a little more busy...

Regards,

Gene
CFII, MEI, ASC

actually I think you would push them up to flight idle just before takeoff..
that's why when your sitting in the back of a turboprop.. you here the
engine pitch change as they taxi onto the runway..

before the power levers come up

BT

"Art Varrassi" wrote in message
news:yJ5Cd.67983$k25.46039@attbi_s53...
Excellent! Thanks. So let me see if I have this right; After engine start
the condition levers would be in ground (low) idle through taxi and
takeoff and I would move them to flight (high) idle at cruise. They would
stay at flight idle through descent, approach, and landing and then moved
to ground idle during thrust reversal in preparation for taxi again. Sound
ok?

"CFII_ASC" wrote in message
ps.com...
Hi,

The condition levers are the analog of the mixture controls. They are
coded the same color (red), and in the same position on the quadrant
(far right) as mixtures, but they actually do not do the same thing as
mixture controls.

A mixture control changes the air-fuel ratio (piston engine). In the
turbine, the condition lever is used to control whether fuel is going
to the engine or not (bottom stop is CUT-OFF). The other two positions
set the idle speed of the engine, i.e. what turbine (N1) speed the
engine will run at when the 'power levers' (those black things that we
call throttles) are pulled back to the idle position. The mixture is
actually controlled automatically by the fuel controller.

So, for example, in a King Air, you have Power Levers, Prop Levers, and
Condition Levers; they look much the same and are in the same positions
as the throttles, prop and mixture controls in a piston twin.

The effect of the condition levers is to either 1) shut off fuel to the
engine (cut-off), or to set the idle governed speed for ground
operations (typically 25% N1), or to set the idle speed for flight
operatons (typically 50% N1). They have these two settings because the
turbines have so much power at flight idle that on the ground you
wouldbe constantly riding the brakes to maintain a safe taxi speed, and
scattering miscellaneous small aircraft in your prop blast as you
maneuvered on the airport. The machine is much easier to manage on the
ground with and idle of 25% N1. However, if we used ground idle in
flight, at idle power the drag on those two huge props would be
excessive, and the airplane would develop a dangerously high sink rate
if the pilot ever pulled back to idle, say on a slightly high approach
on final. Compounding this problem is the long spool-up time the
engine would require if the pilot suddenly decided he wanted power
again after letting the engine spin down to 25% N1 (Remember the Paris
Airshow crash of the Airbus?) So, in flight we keep the condition
levers in the Flight Idle stop, so that if we ever pull the power
levers back to idle on final we won't make one of those big, smoking
holes in the ground just short of the runway.

Right after touchdown it gets a little busy as you come in with the
brakes, pull the power levers up and over their lockouts and back into
the thrust reverse positions; then move back over to the condition
levers and pull them back into ground idle so that once we come out of
reverse we will not have the flight idle thrust fighting the brakes;
but then we have to bring the right hand back over to the power levers
and bring them forward, out of reverse before we get below about 40
KIAS, because at those speeds in reverse the props tend to suck things
up off the runway and get damaged (really expensive) so we put them
forward as we hit 40. While you are doing all of this with your right
hand, your left hand has to be holding the elevator back (ugh) by
itself, your feet have to keep us on the centerline and your toes have
to apply just enough equal braking pressure so that we stop in time,
but not so much that we trigger the anti-lock system and scare all the
passengers.

that's a normal landing... add a slick runway and a stiff crosswind and
you will be just a little more busy...

Regards,

Gene
CFII, MEI, ASC

"Art Varrassi" wrote in message
news:yJ5Cd.67983$k25.46039@attbi_s53...
Excellent! Thanks. So let me see if I have this right; After engine start
the condition levers would be in ground (low) idle through taxi and
takeoff and I would move them to flight (high) idle at cruise. They would
stay at flight idle through descent, approach, and landing and then moved
to ground idle during thrust reversal in preparation for taxi again.
Sound
ok?

http://av-info.faa.gov/data/training...83-3a-6of7.pdf
(Chapter 14)

CFII_ASC wrote:

The effect of the condition levers is to either 1) shut off fuel to
the
engine (cut-off), or to set the idle governed speed for ground
operations (typically 25% N1), or to set the idle speed for flight
operatons (typically 50% N1). They have these two settings because
the
turbines have so much power at flight idle that on the ground you
wouldbe constantly riding the brakes to maintain a safe taxi speed,
and
scattering miscellaneous small aircraft in your prop blast as you
maneuvered on the airport. The machine is much easier to manage on
the
ground with and idle of 25% N1. However, if we used ground idle in
flight, at idle power the drag on those two huge props would be
excessive, and the airplane would develop a dangerously high sink
rate
if the pilot ever pulled back to idle, say on a slightly high
approach
on final. Compounding this problem is the long spool-up time the
engine would require if the pilot suddenly decided he wanted power
again after letting the engine spin down to 25% N1 (Remember the
Paris
Airshow crash of the Airbus?) So, in flight we keep the condition
levers in the Flight Idle stop, so that if we ever pull the power
levers back to idle on final we won't make one of those big, smoking
holes in the ground just short of the runway.

The idle open descent mode on the earliest generation of A320s did
actually set the idle speed to about 25% N1. It was also slightly
misleadingly called a 'power descent' when it was being caused by the
lack of power. Pilots are instructed to use this only during descents
up to the traffic pattern altitudes from TOD and not beyond it. Those
that remember minutiae of the Feb 90 Bangalore crash will recall that
the pilot used this on final, in violation of the recommended
procedure. As the Pratt & Whitneys were revving, the craft had already
created a huge dent on the mound of the 8th hole of the golf course
behind my house. It garnered enough legs to lift briefly beyond the
road adjacent to the golf course before flopping short of the runway.

Actually Gene, the length of the spool-up time wasn't the cause of the
Paris crash, but more so in case of the Bangalore one. In Paris, the
A320 was flying at 30 ft with the landing gear extended, while Cap'n
Michel Asseline (now in jail, incidentally) I remember asserting he'd
seen the altimeter show 100 ft! The computer interpreted this to be a
landing configuration and didn't deliver power to the engines. Asseline
insisted that his manually moving the throttle didn't elicit any
response, so it wasn't the CFM engine not responding quickly enough but
the computer having taken over control.

In any case, a gas turbine delivering 20 meg watts of power can be
expected to take about 10 secs or so to deliver thrust. You folks would
know all that better

Cheers,

Ramapriya

A320 was flying at 30 ft with the landing gear extended, while Cap'n
Michel Asseline (now in jail, incidentally) I remember asserting he'd
seen the altimeter show 100 ft! The computer interpreted this to be a
landing configuration and didn't deliver power to the engines. Asseline
insisted that his manually moving the throttle didn't elicit any
response, so it wasn't the CFM engine not responding quickly enough but
the computer having taken over control.

HAL... give me the computer HAL...

Excellent explanation. I went to KingAir school back in the 70s and got very
few hours in one before my Lear type rating got me away from propellers.

Maybe I was stretching things to even mention turboprops in my multiengine
book. Its target readership is applicants for the multiengine rating, of
course, not rated pilots upgrading to turboprops.

Bob Gardner

"CFII_ASC" wrote in message
ps.com...
Hi,

The condition levers are the analog of the mixture controls. They are
coded the same color (red), and in the same position on the quadrant
(far right) as mixtures, but they actually do not do the same thing as
mixture controls.

A mixture control changes the air-fuel ratio (piston engine). In the
turbine, the condition lever is used to control whether fuel is going
to the engine or not (bottom stop is CUT-OFF). The other two positions
set the idle speed of the engine, i.e. what turbine (N1) speed the
engine will run at when the 'power levers' (those black things that we
call throttles) are pulled back to the idle position. The mixture is
actually controlled automatically by the fuel controller.

So, for example, in a King Air, you have Power Levers, Prop Levers, and
Condition Levers; they look much the same and are in the same positions
as the throttles, prop and mixture controls in a piston twin.

The effect of the condition levers is to either 1) shut off fuel to the
engine (cut-off), or to set the idle governed speed for ground
operations (typically 25% N1), or to set the idle speed for flight
operatons (typically 50% N1). They have these two settings because the
turbines have so much power at flight idle that on the ground you
wouldbe constantly riding the brakes to maintain a safe taxi speed, and
scattering miscellaneous small aircraft in your prop blast as you
maneuvered on the airport. The machine is much easier to manage on the
ground with and idle of 25% N1. However, if we used ground idle in
flight, at idle power the drag on those two huge props would be
excessive, and the airplane would develop a dangerously high sink rate
if the pilot ever pulled back to idle, say on a slightly high approach
on final. Compounding this problem is the long spool-up time the
engine would require if the pilot suddenly decided he wanted power
again after letting the engine spin down to 25% N1 (Remember the Paris
Airshow crash of the Airbus?) So, in flight we keep the condition
levers in the Flight Idle stop, so that if we ever pull the power
levers back to idle on final we won't make one of those big, smoking
holes in the ground just short of the runway.

Right after touchdown it gets a little busy as you come in with the
brakes, pull the power levers up and over their lockouts and back into
the thrust reverse positions; then move back over to the condition
levers and pull them back into ground idle so that once we come out of
reverse we will not have the flight idle thrust fighting the brakes;
but then we have to bring the right hand back over to the power levers
and bring them forward, out of reverse before we get below about 40
KIAS, because at those speeds in reverse the props tend to suck things
up off the runway and get damaged (really expensive) so we put them
forward as we hit 40. While you are doing all of this with your right
hand, your left hand has to be holding the elevator back (ugh) by
itself, your feet have to keep us on the centerline and your toes have
to apply just enough equal braking pressure so that we stop in time,
but not so much that we trigger the anti-lock system and scare all the
passengers.

that's a normal landing... add a slick runway and a stiff crosswind and
you will be just a little more busy...

Regards,

Gene
CFII, MEI, ASC

Bob
BIG differences between the P&W and Garrett!! I've got about equal time
with them and each has its good and bad. Good training is the key to
using either of them properly and safely. I've done FSI for both in
flying the King Air series from 90-200, and in the Swearingen Merlins.
Cheers
Rocky