Instrument approach speeds and manifold settings for J owners

[RobertE]

I'm wondering what manifold settings and resulting approach speeds others use.  Specifically, what settings do you use during the initial segments and, if different, during the final segment?

[ArtVandelay]

I use 18", gets me down to about 120, well below Vge.

[aaronk25]

It varies and MP gauge can vary at least 2" or more between planes. But last night did a approach to min coming into Nashville in my 77j.

Rough outline what I've done:

Slow to gear ext speed at or before the last vector to approach. 20" mp

Drop gear at FAF, power to 16mp no wind or 19-20 if head wind. At 18" mp it will slow enough to extend flaps after about 25sec or so, which is just after FAF, so gear out at FAF.

To be honest though to keep things simple most of the time I don't drop the flaps to keep it simple until breaking out as even at MIN there is a lot of time to get the flaps out.

Never full flaps on approach as it only allows for a Knot or 2 slower speed but create a issue with nose up on full power go around and requires retracting them fast on go around. 1/2 flaps (take off flaps) at most for approach if any at all.

So in short find a setting that maintains you 100-110kts on the glide slope, 15-20", depending on 1/2 flaps or no flaps. But giving you my exact mp is kinda worthless as yours will be different I guarantee it.

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[201er]

18 minutes ago, RobertE said:

I'm wondering what manifold settings and resulting approach speeds others use.  Specifically, what settings do you use during the initial segments and, if different, during the final segment?

Good question/bad question. The most accurate answer is it varies by situation.  But, I understand how unhelpful of an answer that is so I will give some ballparks that may help illustrate where my "it varies" falls.

During the initial portion of the approach I like to slow about 120kias. Usually a reduction to about 22 squared (only for purpose of easy memory and no particular reason) and lop to about 6-7gph (45-55% power). I don't like flying approaches faster than that because things happen quickly and mistakes get amplified. Slowing up for an approach provides more time for more thoughtful operation. On the flip side, getting slower makes the plane a bit more mushy and less spritely. 120kts also happens to be my preferred downwind speed. Furthermore, this is my preferred gear extension speed. This way even if I forget to check that I'm within gear extension speed or get a little faster, I am still within gear extension speed.

At the FAF it's gear down, takeoff flaps, trim, and GUMPS. Without a power change this will naturally slow me to about 90 knots which is a good safe initial final approach speed. I usually don't go flaps full till I see the runway and am ready to add the flaps.

Just like on a visual approach, I begin a gradual slow down on short final and transition to flying by AOA using the AOA indicator as my primary instrument and speed becomes secondary in my mind. By the time I pop out, my speed should fairly well resemble what it might be on a visual approach but a tad faster (5-10knots). There are no fixed speed numbers at this point because I am flying based on a familiar angle of attack (speed varies based on weight and other factors). Pop out, drop flaps, normal landing.

Edited January 14, 2017 by 201er

[aaronk25]

201er made a good point about flying the approach at a fast enough speed so the plane isn't mushy. So important it increases the pilots work load dragging a plane down the glide slope. Keep it fast enough so the wing is flying clean and also a fast enough speed helps reduce side to side yaw.


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[carusoam]

One place you can find power settings is a really cool document printed by MAPA.  It is a handout provided during their PPP training.

Best regards,

-a-

[MooneyBob]

18"MP/2500RPM between IAF or IF and FAF. Flaps and gear still up. Confirmed speed around 110-115knts usually already leveled at the FAF altitude. 

Drop gear and half flaps at FAF.  GUMPS. It slows me down to around 90-95knts and 500 ft/min descent to stay on the GS. Trim to maintain the speed and adjust throttle to stay on the GS. Usually it requires minimum adjustments. Maybe pull back to 17".

GUMPS. Further action depends on the altitude I broke out, wind and my mood. Usually it takes 13" on short final to slow down and trim for nice regular landing. GUMPS. Touch down. 

 

[ArtVandelay]

18"MP/2500RPM between IAF or IF and FAF.
 

Why such a high RPM if you want to slow down?

[gsxrpilot]

I'm with MooneyBob on the procedure here.  And by the way, I'm not relying on the prop to slow me down. With the prop RPM higher, it's ready in the even of a go around.

[MooneyBob]

Good question. I don't really have a problem to be at the right speed with this RPM setting. But in my mind in the case of sudden missed approach I am ready to climb. But it's me. Unless it's totally wrong and dangerous. 

[carusoam]

Thought provoking ideas....

High rpm braking is more noticeable when the MP is really low when the prop is pushed all the way in...

there is an automotive almost equivalent...  like cruising a 60mph and selecting 2^nd gear...engage the clutch slowly to allow the engine revs to catch up... dumping the clutch too fast, the wheels don't stay attached to the pavement, and vehicle control starts to get elusive... doing this in first gear would lead to exceeding redline while letting the clutch out...

with the airplane,  the engine is always connected, there is no clutch.  The cylinder compression supplies a lot of breaking power.

Odd failure modes to consider...

1) If the air can't stay attached to the prop it would stall.  

2) If the prop goes to the stops and the plane is in a descent, a steep one, would the engine get over driven beyond the 2700rpm redline before stalling?

being ready for a go around is within the normal operations of the airplane.  Exceeding red lines would need to be addressed.

Some prop and airframe combinations have limitations placarded on the IP.  These need to be considered as well.

PP ideas only, not a CFI.

Best regards,

-a-

Edited January 15, 2017 by carusoam

[ArtVandelay]

The car analogy doesn't really apply, tires are physically connected to the ground, the prop is not. If it was we would shift gears, instead the prop RPM can remain the same whether taking off at 0 mph or at 175 mph.

The flatter prop will provide braking but only when power is reduced to the point that full RPMs can not be maintained because power is low.

We're talking about power settings on the approach between IF-FAF, no need to be in go around mode at that point.

When you want to fly faster (more power), you increase RPMs, seems to me the opposite should be true.

Look at the POH, for the same MP settings, you fly faster at higher RPMs.

Just seems counterintuitive, here is an idea...next time y'all go out and fly, try reducing RPMs on descent, see how it works for you.

[midlifeflyer]

Drilling down to some related detail. Before breaking out and assuming an approach to minimums:

1. Are you using approach flaps or not? And if you are, when do you deploy them?

2. Are you using a decelerating approach? If so, what is your technique?

[kevinw]

I always use approach flaps. I slow to about 120 using 20" and 2400 rpm. Sometimes 18" if I'm coming in a little fast. When the glideslope indicates a dot and a half I drop the gear. This slows the plane to about 100 by glideslope intercept which happens about 10 seconds later and at this point it's flaps to approach and power to 15" which puts me at 90 knots on the approach. Then gumps, full flaps when I breakout and touchdown.


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[rbridges]

same ballpark as everyone else.  I'm usually 19" through the approach.  I vary it as I get closer to the FAF.  I was taught to have gear down, initial flaps before crossing FAF, so I adjust MP to get me to flap speed.

[cnoe]

As others said, there are many variables but most of us find a range of settings that work for us. Obviously at a busy field with approach saying "maintain best speed" my technique differs greatly from an approach to a lonely uncontrolled field. The DPE who did 3 different checkrides with me preferred that the plane be slowed down with approach flaps deployed by the IF. For a relatively new instrument pilot like me (2 years IR) it's simply much easier to nail the approach at Vfe than Vle. I'm also a fan of the 2,200 rpm setting and before reaching the FAF I usually slow further to 90-95 kts (not mushy). At the FAF the gear drops and power is set/reduced to maintain a stabilized approach speed of 85-90 kts. Once the power is reduced GUMPS is repeated with prop going full-forward (since it's already on the stops by that point anyway). I'm a big fan of stabilized approaches and don't "decelerate" on the glideslope in IMC; I prefer to be "on speed" the whole time. I can slow to Vs0 x 1.3 after I break out. Lastly I don't use full flaps unless I absolutely have to as it just complicates matters in the event of a go-around (isn't every IFR approach a planned "miss")?

Those with 10X my experience may employ different techniques but this works well for me.

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[Piloto]

Power setting will vary according to aircraft weight and configuration. I aim for 80kts at 1,000ft and 3nm from runway end  from that point on flaps down, gear down and throttle back gradually to 70 kts. On the flare at 5ft or less AGL I  raise the flaps on gusty or crosswind conditions.

José

[ArtVandelay]

At 2000 rpm and 17" I would be doing 113 knots in level flight, y'all must be pulling back power to get such slow approach speeds. I prefer 100 knots at FAF, it's more responsive and gives me a greater margin of error in case of wind shear. Only after breaking out do I slow it down for landing. I've had the stall horn squawk once on in IMC while getting bumped around, now I keep my speed up.

[carusoam]

TJ,

The higher rpm situation that I described is counter intuitive for most.  That's what makes it interesting...

1) As long as the cars tires maintain contact with the ground without skidding they provide braking power... if they skid the tail end of the car washes out and an exciting ride will ensue... (rear wheel drive of a Firebird used as an example)

2) As long as the prop maintains aerodynamic lift ( like a wing) , it can provide braking power...  I have never felt the prop lose lift or stall.  Technically it should happen at some speed....?

3) it is pretty easy to find the point where the prop is driving the engine.  This is when braking occurs. During the first GUMPS check in the pattern when pushing the blue knob all the way in, the seat of the pants feel is braking...

4) use caution to not slam the prop into full braking mode. It would be like dumping the clutch. An over-rev situation could be induced depending on the mechanical gov's abilities to control the prop pitch...

5) use caution if setting prop rpm to balance power in the middle zone.  I would expect the people that don't like pulling and pushing a plane by its propellor on the ground will be screaming out in unison...

6) I used the MAPA recommendations while flying IFR... combined with Mooney efficiency standards... no added air resistance until required.  In IMC, safety by following known procedure is all I have...

This list is intended to clear up my thoughts from the previous list... writing can be challenge to get some ideas conveyed...

I only used the automotive idea to attempt to describe engine braking.  Unfortunately, that didn't help very much... the only other time engine braking is used (that I know of) is in large trucks when they use a Jake brake. A more complex mechanical situation but a really good use of thermodynamics in the real world.  Compressing air in the cylinders generates a huge amount of physical resistance followed by dumping it out the exhaust pipe....

Wait, there IS more...

A modern way to look at this is with electric cars that use the electric motor to slow the vehicle down.  The regenerated power gets stored back in the battery for re-use.  Much better than a Jake brake that dumps the stored energy back into the atmosphere.  

Best regards,

-a-

Edited January 15, 2017 by carusoam

[bradp]

I have never used a set of numbers for power settings for instrument approaches. Just generalized ballparks. I slow to desired indicated speed (depending on what category I want my approach speed to be at) prior to IF/intercept point. The power down to maintain the desired descent rate accounting for groundspeed / wind and pitch for the target airspeed. Memorizing a bunch of target MAP/RPM seems over doing it to me.

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[midlifeflyer]

Just now, bradp said:

I have never used a set of numbers for power settings for instrument approaches. Just generalized ballparks. I slow to desired speed (depending on what category I want my approach speed to be at) prior to IF/intercept point. The power down to maintain the desired descent rate accounting for groundspeed / wind.


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For those who do use sets of numbers, they are just tickets into that ballpark.

A pre-solo student pilot who reduces power to 1700 RPM abeam the numbers in a Piper Cherokee as part of starting the descent to the runway is using the same type of tickets.

[ArtVandelay]

TJ,
The higher rpm situation that I described is counter intuitive for most.  That's what makes it interesting...

3) it is pretty easy to find the point where the prop is driving the engine.  This is when braking occurs. During the first GUMPS check in the pattern when pushing the blue knob all the way in, the seat of the pants feel is braking...

A better analogy would be letting your foot off the pedal , reducing power.
Braking causes the car to stop, reducing power just causes it to slow down.
Lower RPM for the same MP results in less power, better for slowing down.

[Andy95W]

I think both you and Anthony are correct, but maybe in different ways. 

In a big turboprop, going to fine pitch and idle power increases drag A LOT, so I think Anthony is correct from a theoretical point of view. 

In our airplanes, however, we really can't go to a true flat pitch on our props, and it is not recommended to let the prop drive the engine at a deep idle, so in our airplanes the drag increase either isn't significant or not attainable. 

Just my $.02

[DonMuncy]

I think I misspoke in an earlier post. I said if the regulator valve was shutting off, and still losing pressure, it had to be a tank leak. I forgot about the filling valve. It is on the high pressure side of the regulator, and could be leaking. Try not to let it be that. That valve costs about $300.

Sorry. wrong thread.

[carusoam]

5 minutes ago, DonMuncy said:

I think I misspoke in an earlier post. I said if the regulator valve was shutting off, and still losing pressure, it had to be a tank leak. I forgot about the filling valve. It is on the high pressure side of the regulator, and could be leaking. Try not to let it be that. That valve costs about $300.

Don,

I think your post got misplaced...?  

Sounds like an answer to the O2 tank leak somewhere in a different thread...  

Best regards,

-a-