Hi, have just joined COPA. I am doing my instrument rating in my SR22 in Australia with a non-Cirrus instrtuctor. I am trying to find a good power setting for instrument approaches that keeps the speed back but doesn’t over cool the engine. can anyone hlep with suggested settings? look forward to some help dmoore
I use 18in MP (45% power) = 120 KIAS and make sure i am there in plenty of time to put in 50% flaps 2 miles before FAF. Then down to 12in MP (30% power/50% flaps) for a 500fpm descent after the FAF. Works for me but yours may vary. i suggest trying it out a few times VFR with a safety pilot to see what works for you. Remember to set the power and leave it alone.
1st; Welcome mate
Next; Use the “search” function. it’s the Aladdin’s lamp of the aviation internet. Everything has been answered just waiting for you to hit “search”
Next, what’s this about overcooling your engine?
Next: 19" and 12" will get you what you want.
Hi David, I got my IFR ticket a few months ago and have been playing with the settings too. I also seeked COPA help in previous posts. I fly in Europe in busy airspace where ATC (often) keeps you high and fast. My personal considerations are:
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Cirrus planes don’t like high and fast, so don’t be: either high or fast, not both
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Cirrus planes don’t like slowing down while descending: put the nose down and wait for IAS to get to 119 KIAS? good luck.
I have tried leveling off from a 180 KIAS 600fpm @ 18MP descent to see how long it takes for the plane to slow down, well at 3NM per minutes it goes a long way.
What I do now is I plan my descent way in advance, backwards: my actual FL minus the required FL times 6. Example: Cruise FL 120, FAF 4000ft -> 12-4 =8, 8*6= 48NM (!) Which means 48NM before the FAF I start a descent with 180KTS GS at 600 ft/min (that is 3NM/min). It is a shallow descent angle, at 180KTS you should make 900ft/min for 3deg slope, but I find this rate not acceptable for my passengers. If ATC doesn’t let me get down: well, I slow down (in level flight, 1"MP/min) to 119KIAS. With a notch of flaps I can now descent 600ft/min, the additional drag keeps the IAS below flap1 speed and I still have some MP (12") in to keep my CHTs in the green. Try do descend faster and watch the IAS go up and your flaps go bye bye [:)] Any “intermediate level off” for ATC reasons calls for an increas in MP, but I keep my flap 1 out and my speed down
If ATC “asks” me to mantain high speed (160KTS=800ft/min @3deg) is mostly on big airports with long runways so (if the weather is good!!) I give them what they want 'til the OM and use the runway to “slow down” and make a long landing.
All these considerations are personal, I would never dare to “teach” anything in a COPA forum, it’s what I do and it works out pretty fine. I am looking fwd to read what fellow pilots think about this…
Ciao
John
Hi David,
First let me suggest that as a member of COPA you post on the Member’s Forums where you will get far more responses.
Next I have to tell you that here in the US most pilots regard the phenomenon of “shock cooling” as pretty much of an old wives tale. The engine cools quite quickly when you shut it down and it heat up even faster when you start it and those temperature differences don’t seem to cause issues.
For normal approaches I will pull the throttle back to just below the detent, then push right up to the detent when I want to begin to slow. This usually puts me at 20 inches MP. The IAS that gives me varies with temperature and altitude but it usually is in the 130 KIAS range. As I get closer in I pull the throttle back to the bottom of the green arc and that will always put me at an airspeed where I can deploy the first notch of flap. Once I’m there I use throttle as necessary to maintain the speed I want (for an ILS that’s 105-115 KIAS) Often that will require about 12-13 inches MP in the descent. If I get too fast I pull the power back without looking using the airspeed indicator as my primary power instrument. If I get too slow I add power. When the runway is made I pull the power back, add full flaps when speed permits and land.
For a fast ILS at a busy airport I’ve taken to let the autopilot do the work. I maintain cruise power and allow the autopilot to track the glideslope. About 2-2.5 miles from the runway I pull the power back to idle and allow the AP to track the GS while the airplane slows (and it slows rapidly at idle). Then when the speed gets to 119 I add 1/2 flap. The plane will continue to slow. When it reaches 100 KIAS I disconnect the autopilot, put in the rest of the flaps and land. This is an effective technique but some passengers may find it uncomfortable because of the sensations of the rapid decelleration.
There are many variations on the above theme but all of them have you making some fairly drastic power reductions quickly. Most of us do not feel there is any harm in doing so.
One thing I do is warn all new passengers of three things that may be scary: 1, and appropriate for this discussion, is I tell them I often pull back the power and they’ll feel the plane slow down and get quiet. 2, traffic alert. 3, autopilot disconnect.
I just warn my passaengars of one thing. If they barf without using a barf bag, it’s a long fall to the ground.
17 MP to maintain 120 kts straight and level, 11 MP with 500 ft descent to maintain your glideslope you can varied depend on your descent rates. It will work as magic.
I have to agree (at least for my 2004 G2) - 17 inches MP gets me 118-120 level all the time. 11 inches for 500fpm downhill with one notch of flaps. Dead nuts.