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Technique for descending from altitude

Mdragon

Active Member
I’m a new pilot and new RV9 owner. I’m still trying to figure out a good technique for a nice controlled descent into my destination airport. I’ll be cruising along at 170 mph, say at 4500 feet, and then have trouble losing the altitude and speed by the time I get to the pattern. I have a fixed pitch prop.

What do most of you do to gradually bleed off speed and altitude? Any particular rpm, TAS?

My plane just want to glide and glide and keep its speed.
Not a bad thing, but haven’t quite figured it out yet.
 
Use your Vnav to configure your descent. If I’m getting a good tailwind and temp up high I’ll stay up longer and use 800-1000 fpm. If I wanna leave the power in and and pick up speed in smooth air I’ll use 200-400 fpm. Both cases I aim to be at pattern Alt 3-5 miles out with an incremental pull to idle as I level over a couple miles sets me up nicely for flap speed as I approach the pattern.

Using C172/Pa28 power settings for the pattern in an RV won’t work, if your at 160 knots/level just off idle a mile or so from downwind should set you up close.
 
Here is a simple technique:

Take your current altitude and subtract the altitude to loose and divide by 500 fpm. That is how many minutes out you should start decending.

Example: cruising at 9500 feet, pattern altitude is 2500 feet. Altitude to loose is 7000 feet. Divide that by 500 = 14 minutes.

Add about 2 minutes for the slow down. So 16 minutes away from the airport at cruise speed/altitude start your decent at 500 feet per minute and you'll arrive at pattern altitude about 3 miles before your airport, which will allow you to slow down and enter the pattern.

Whats awesome is all you need to do is throttle back a little, no need to touch the trim. This keeps the engine from cooling too fast and also allows for a nice comfortable decent.

Sometimes it's surprising how early you have to start down. The other day I stated down 40 miles out and thought "that can't be right" but with a good tail wind and alot of altitude to loose it was infact correct.
 
Agreed

I agree VNAV is your friend. I set mine up for 500 fpm 1000 above waypoint and a couple miles before waypoint. You’ll get an approaching VNAV message, activate it and if you don’t have an autopilot on follow your VNAV indicator. Easy Pasy :)
 
One subtle thing is that as you descend, the manifold pressure increases as the air gets denser. For a fixed-pitch prop you'll probably see that as increased rpm. With either prop, you need to gradually reduce throttle as you descend.

Don't forget to increase the mixture, too, if you've leaned for the cruise.

Dave
 
My easy rule of thumb is to plan for 5 miles per 1000' of descent. I just trim to 500' per minute descent and pull back the RPM's from cruise (around 2470) to 2200 RPM. If I'm cruising at 147-150 Kts, then without pulling the power I'll be easily doing 155+ Kts, which is fine if the air is smooth. Once I hit the Delta airspace (4 miles out), I can throttle way back to 1500-1700 RPM in order to slow down and fine tune the descent to pattern altitude.
I also will put the pattern altitude into the EFIS. On the Skyview, it will show an "arc" on the screen where you will hit that altitude. The EFIS will also give you VS guidance to meet that altitude at your waypoint.
If you really need to slow down in the RV-9A, throttle to idle and keep holding altitude. Several miles later you'll be at Flap speed. :)
 
I’m a new pilot and new RV9 owner. I’m still trying to figure out a good technique for a nice controlled descent into my destination airport. I’ll be cruising along at 170 mph, say at 4500 feet, and then have trouble losing the altitude and speed by the time I get to the pattern.

Easy head math. Multiply altitude above pattern x 2 x miles per minute to know how many miles out to start a standard 500 FPM descent. In your example you want to lose 3.5 thousands while traveling at almost 3 miles per minute. So, 3.5 x 2 x 3 = 21 miles. 150 mph would mean 3.5 x 2 x 2.5 = 17.5.

Normal part of the RV transition for many.
 
My goal is to be at 90 kt and pattern altitude 10 miles from the the airport and entering the VFR approach I've put into Foreflight (which in turn has been sent to my EFIS over wifi). I use an app called Descent Calculator. For me, it simplifies the math but if you're really smart, you can do it in your head. At the appropriate calculated distance out, I pitch at about -2.5 at 20 inches and 2300 RPM, which usually gives me -500 FPM. Airspeed is whatever. If I'm that high, I pull back to 2100 RPM and will pitch for 1000 FPM. When I hit pattern altitude, I come back to 15 inches and 2100 RPM, and at 90 kts will put in 10 degrees of flaps. I fly 90kts into downwind and then will slow to about 80 kts and put in another 10 degrees of flaps. Once I turn final, I'll be at about 70 kts and adjust power appropriate to my landing spot.
 
As mentioned plan ahead and come down at a nice pace. For me I have the dynon HDX and it will show me what FPM I need to decend to get to pattern altitude, when it gets close to 500 I set A/P or trim to attain that.

Best way I have found in the 9 to loose altitude close in, and not gain speed is to get it slowed down first, point it down and you will just convert altitude to speed. Slow it down to flap speed, get the flaps out, keep it slower and it will come down much better.
 
My goal is to be at 90 kt and pattern altitude 10 miles from the the airport ...

That strikes me as unnecessarily low for that far out.
1. I try to descend at a rate that gives me a chance of making the airfield if the engine should quit.
2. 700’ or 1000’ over a city or town 10 miles out just creates ill-will from non-pilots, and may even be an far violation.
3. My home field is in a valley. 10 miles out at pattern altitude puts me underground!
 
That strikes me as unnecessarily low for that far out.
1. I try to descend at a rate that gives me a chance of making the airfield if the engine should quit.
2. 700’ or 1000’ over a city or town 10 miles out just creates ill-will from non-pilots, and may even be an far violation.
3. My home field is in a valley. 10 miles out at pattern altitude puts me underground!

No valleys here in Minnesota.:)

I'm guessing that as I get more experience with this airplane, I'll shorten up those approach distances.
 
Here's what I do:

Cruising alt - traffic pattern alt (5500-1000= 4500)

Then /500fpm (4500/500=9)

9 minutes out I need to start my decent. I use either the ETA in the 430 if I'm using it. Or the two-finger ruler on FLYQ which gives time as well as distance. I also have the 5 min course line on my moving map so I can estimate.

This errs on the side of being a tad high by the pattern but it works well for me to drop in on a downwind. It is dependent on a moving map though.

Which I also see is described in the 3rd post lol.
 
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Here is a simple technique:

Take your current altitude and subtract the altitude to loose and divide by 500 fpm. That is how many minutes out you should start decending.

Example: cruising at 9500 feet, pattern altitude is 2500 feet. Altitude to loose is 7000 feet. Divide that by 500 = 14 minutes.

Add about 2 minutes for the slow down. So 16 minutes away from the airport at cruise speed/altitude start your decent at 500 feet per minute and you'll arrive at pattern altitude about 3 miles before your airport, which will allow you to slow down and enter the pattern.

Whats awesome is all you need to do is throttle back a little, no need to touch the trim. This keeps the engine from cooling too fast and also allows for a nice comfortable decent.

Sometimes it's surprising how early you have to start down. The other day I stated down 40 miles out and thought "that can't be right" but with a good tail wind and alot of altitude to loose it was infact correct.

This is just about exactly my usual strategy, and I can use the altitude intercept arc to fine tune it. I try not to shock cool my engine if possible, so I slowly ease off my power during the descent until I am just about at my pattern RPM as I level off a mile or so from the pattern.

As you get more comfortable in the plane you will get a better feel for when and how to start the slow-down process, but since every RV is different you will have to find what works for you - a good excuse to fly more.

Chris
 
You've clearly asked a question that every RV pilot needs to find their answer for since we don't land at speeds or altitudes that we cruise at. In fact a drop from ~140kt to ~60kt is a massive change that is both the blessing and the curse with these amazing planes. Answers here have been around descent planning and have been variations of the similar. One thing I didn't see though was taking advantage of the single best opportunity to lose speed (I saw one similar thought).

My transition trainer taught me to reduce power (10" in a C/S, nearly idle) for the descent to pattern altitude and then intercept that altitude with a 1 degree nose up attitude. Hold that attitude and altitude down to 90 kt, it will slow quickly and smoothly. When you hit that target, ease in a bit of power (13") and settle in at ~85kt. Then trim to lock it all in. Sorry this is for a C/S prop so no target RPMs, but it also isn't using the C/S prop to slow down so it should work great for you too.

I got away from this in my early days on my -9a, and forced myself back to something similar to this. Key point is timing my speed reduction with a level out by adding a little extra nose up. Works every time, even when I leave it late. I sometimes kick myself for missing this opportunity and finding myself without any altitude to lose and lots of speed to lose. Sure you can still do it by the same method you would enter slow flight, but the pattern altitude method is nearly effortless.

Other suggestion is practice slow flight at altitude often. The goal is to get really comfortable at speeds under 65 kts because you will want that dialed in for your landings.
 
Take your altitude in thousands of feet above traffic pattern altitude, multiply by 6. This is the distance from the airport you need to start your descent at 500 fpm. Actually at 175 (vs 180) you’ll be down slightly early - might be a good thing. With a tailwind, start down a mile or two early..... headwind, delay that descent for a mile. For example, heading in to an airport with a TPA of 1000’, you’re cruising at 4000’; 3 X 6 = 18 miles - where you need to start your descent at 500fpm. As you descend, reduce power to maintain your cruise airspeed. We aren’t concerned about manifold pressure for the remainder of the flight - normally. Entering the pattern, reduce RPM to 1500-1800. Plan to be on a mid field downwind at 100K. By now you know how well these fixed pitch RV’s glide. Idle power abeam your planned touch down point should get you to your flap speed by the time you are ready to turn base. Stand by for a perfect landing....
 
One question......multiple right answers....

here´s mine. Will work on every aircraft, not restricted to single type.

Altitude to loose in thousands of feet (or flight levels) multiplied by three will give you the distance out from your "bottom of descent".

Groundspeed (knots) multiplied by five will be your descent rate in fpm (which will give you a 3 degree descent angle).

Example:
6000 feet to loose, start your descent 18 miles from the point you want to be at the lower altitude.
150 knots GS will result in 750 fpm descent rate.

What i like on that "formular":
-as you take GS, head- or tailwind is already included in the math.
-works on every powersetting, airspeed, RPM, whatsoever…..
-you only have to monitor/adjust your rate of descent, nothing else, to be at the new altitude at the position you choose.
-if you calculate distance out from your destination, you come in perfect for a overhead break (if traffic permits)
-simple add 2 miles to bring back the speed when you want to enter the traffic pattern (listening to the radio will show you which option is the better one to choose)


But other ideas and procedures are as good as mine……
It will be yours to choose your favourite.
 
Descent to destination is one of the flight regimes that I really like with a CS prop since high power can be used. If you are ahead of the airplane via one of the mental math tricks already mentioned it is easy to do.
I usually give some nose down trim to hold 500 fpm and watch the speed creep into the yellow but not over TAS Vne. If the engine perhaps roughens from going too far LOP, a turn on the mixture knob. When nearing the desired altitude and position, the throttle starts coming back. The engine is already somewhat cooler because of the higher airspeed descent. In my commute, the larger altitude drop is on the morning eastward leg. You can imagine some phenominal ground speeds aided by common westerly breezes.
 
The IO-390 op manual talks about cooling. Specifies to keep manifold pressure >15 to maintain engine temp in prolonged descent.
 
Here is a simple technique:

Take your current altitude and subtract the altitude to loose and divide by 500 fpm. That is how many minutes out you should start decending.

I curise around 160 knots and usually descend at 170. I use the 6 mile per 1000 feet rule. 500 FPM decent requires 6 nautical miles of distance to lose 1000 ft at 180 knots. Knowing the altitude to lose makes it easy to determin how many miles out to start your descent. My EFIS gives me the banana that shows where I will hit my target altitude and adjust FPM to match, if necessary.

You can determine the miles by the GPS or by using the sliding ruler on foreflight. I use the latter when determining when to start a descent to get under the Bravo at ORD, as there are no waypoints for that.
 
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I like #16's technique, altitude to lose time 3 equals the miles from airport to start down. Example: Your are at 10,000 feet, airport elevation is 1000 feet, the altitude to lose is 9000 feet. Multiple 9 x 3 = 27 miles out start down at 1000 fpm. Adjust as necessary to maintain a 3 degree GS, GS,VS or AS. At 25 miles out, you should indicate 8500 feet, 3 x 25 =75 + field elevation = 8500 feet . Adjust pitch more or less to hit 20 miles out at 7500 feet and so on. This technique kills the wind, SM vs NM, and GS variables. I ignore the pattern altitude until in closer and use it to slow down before entering the pattern. It works for my -9A, and I used it when I worked for Uncle Sam, KC-135s and KC-10s. I was taught not to make it overly complicated, if you can't use it in the cockpit, on the fly, find something else. Dan from Reno
 
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Forward slip

Nobody has mentioned forward slipping yet which is a good tool to have available in the9a with fixed pitch prop I have to demonstrate it along with no flap landing at every bfr. The 9a likes to do this; if you are close in and high use about 70 kts and idle power with or without flaps. Your 9 will sink just like a 6.
 
Personally I recommend taking the square root of 3, multiply times pie and divide by 2.8. Apply that to your imagined altitude and then close your eyes.
 
I like 300 ft/min descents because it's easier on the ears. One time when high and with a very good tail wind, flying West to East, I began my descent to Cincy on the East side of Illinois and descended at 300 ft/min across the entire state of Indiana.
 
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I like #16's technique, altitude to loose time 3 equals the miles from airport to start down. Example: Your are at 10,000 feet, airport elevation is 1000 feet, the altitude to lose is 9000 feet. Multiple 9 x 3 = 27 miles out start down at 1000 fpm. Adjust as necessary to maintain 3 degree GS. At 25 miles out, you should indicate 8500 feet, 3 x 25 =75 + field elevation = 8500 feet . 20 miles out equals 7500 feet and so on. This technique kills the wind, SM vs NM, and GS. It works for my -9A, and I used it when I worked for Uncle Sam, KC-135s and KC-10s. I was taught not to make it overly complicated, if you can't use it in the cockpit, on the fly, find something else that works. Dan from Reno

I use this in pressurized planes.. 3 times the altitude to lose for distance out (when to start down) and 5 times the ground speed for the required descent rate. 300 knots gs and you use 1500 fpm.

For unpressurized planes, I prefer the 500 fpm descent rate method where you double the altitude to lose and convert that to minutes from destination.
 
I like 300 ft/min descents because it's easier on the ears. One time when high and a with a very good tail wind, flying West to East, I began my descent to Cincy on the East side of Illinois and descended at 300 ft/min across the entire state of Indiana.

Easier on the ears, and in the summer you can stay up in the cool air longer.

Coming back from the west I often start my descents for Indy in western or central IL. Always makes me feel like an airliner starting down from so far out :D
 
I like 300 ft/min descents because it's easier on the ears. One time when high and a with a very good tail wind, flying West to East, I began my descent to Cincy on the East side of Illinois and descended at 300 ft/min across the entire state of Indiana.
Steve, FYI, I think it is still illegal to be high in Indiana. Never know, laws could change in the future.
 
So....is shock cooling a real thing? Or yet another aviation old wife's tale?

Are you restricted from flying though rain? That's your answer. But that's not to say that hard temp cycles don't have a price. I just think it is often overblown.

As for cruise descent, there are as many different techniques as there are cross country trips. If no terrain, airspace, wind, or temperature considerations, I come down at 200 fpm. An efficient way to recoup your climb energy.
 
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500fpm + one minute of slow down.

I had the same issue going from 172s and Warriors to my 9a. I use 500fpm for the difference between cruise and pattern altitude, convert that to minutes, and add a minute or two for slowing down and spacing adjustments. I descend with a small pull of maybe 3” of MAP and leave trim right where was for cruise and leave mixture at LOP until I start slowing down. I was taught to get there fast with as much altitude and speed as you can safely carry. KLPR is under class B of CLE, so I can only do so much.

It works on moderate traffic days. On heavy traffic days, I admit to slowing down about five miles out with a trim/throttle dance, again holding a modest descent, in this case I may come into the forty five about 500 ft high and bleed that off in the midfield downwind join. All basic stuff. “If the engine quits now, can you make it?” I want to answer yes, obviously.
 
Steve, FYI, I think it is still illegal to be high in Indiana. Never know, laws could change in the future.

I was high above Indiana, not actually "in Indiana". the descent was faster than shown here. RPM was 2250. 600 nm trip in less than 3 hrs. I really hate days like this. I think I passed over Indiana in 30 minutes or so drinking my cafe latte.

IMG_20180306_094519.jpg


***************

give yourself a big state like Indiana to get down.

high_and_fast.png
 
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I like #16's technique, altitude to loose time 3 equals the miles from airport to start down. Example: Your are at 10,000 feet, airport elevation is 1000 feet, the altitude to lose is 9000 feet. Multiple 9 x 3 = 27 miles out start down at 1000 fpm. Adjust as necessary to maintain 3 degree GS. At 25 miles out, you should indicate 8500 feet, 3 x 25 =75 + field elevation = 8500 feet . 20 miles out equals 7500 feet and so on. This technique kills the wind, SM vs NM, and GS. It works for my -9A, and I used it when I worked for Uncle Sam, KC-135s and KC-10s. I was taught not to make it overly complicated, if you can't use it in the cockpit, on the fly, find something else that works. Dan from Reno

Yep, that’s pretty much what I recommended, except I was recommending a more comfortable 500 fpm descent, so 6 is the multiplier rather than 3. You can do whatever you want. Somebody else was in the middle at 750. You should try to get comfortable with figuring variable rates for time/efficiency reasons. If you are enjoying a tailwind up high that you know you are going to loose in the descent, and your ears can handle it, go for the 3:1. If you are flying into a headwind that will diminish as you descend and you can realize a slightly higher ground speed as you descend, use the 6:1. Or try anything in the middle. In terms of time/fuel burn, the differences are really very small in our small airplanes. I look for ride comfort #1. If I have to endure an increased headwind to fly in smooth air, I’m almost always in favor of that. It usually doesn’t add even 5 minutes to the stage lengths I typically fly, and it’s worth it.
 
Here is a simple technique:

Take your current altitude and subtract the altitude to loose and divide by 500 fpm. That is how many minutes out you should start decending.

Example: cruising at 9500 feet, pattern altitude is 2500 feet. Altitude to loose is 7000 feet. Divide that by 500 = 14 minutes.

Add about 2 minutes for the slow down. So 16 minutes away from the airport at cruise speed/altitude start your decent at 500 feet per minute and you'll arrive at pattern altitude about 3 miles before your airport, which will allow you to slow down and enter the pattern.

Whats awesome is all you need to do is throttle back a little, no need to touch the trim. This keeps the engine from cooling too fast and also allows for a nice comfortable decent.

Sometimes it's surprising how early you have to start down. The other day I stated down 40 miles out and thought "that can't be right" but with a good tail wind and alot of altitude to loose it was infact correct.

I was taught this early on. It works great most of the except when dealing with weather or ATC keeps you high until you are 10 miles out.... :rolleyes:
 
There is another effective descent technique, with the speed staying well below Vne... it's called the spin... :D
 
Descent....and decorum in the pattern.....

I was high above Indiana, not actually "in Indiana". the descent was faster than shown here. RPM was 2250. 600 nm trip in less than 3 hrs. I really hate days like this. I think I passed over Indiana in 30 minutes or so drinking my cafe latte.

give yourself a big state like Indiana to get down.

DANG, I like these airplanes!!

I'm a 500 fpm fan as it is easier on the ears (and engine, I believe). Ears: especially if I have a passenger. So the "altitude to lose/500 = minutes" is a good rule. And it does make you feel like a 737 on descent. ;);) "Ladies and Gentlemen, we are beginning our descent for.........."

Pulling the power back with my Warnke "Almost Constant Speed" prop works as a good speed brake as well if I need that. (LOVE that prop....)

While we are on the subject, it is a temptation with these (and other) fast airplanes to come screaming into the pattern. Flying at a reasonable speed (as these airplanes do so well) is a much better option. I live at an airport and frequently witness high-performance aircraft (did I mention the "C" word?) that come roaring onto the pattern on downwind, then bust the Class D airspace 1.5 miles to the South going from their WIDE downwind to base. Not necessary...and dangerous for multiple reasons. There were 250 incursions of the Class D in October last year. S L O W D O W N.....you sometimes don't know who is in the pattern with you.....or where they are if you do......

Michael
RV-4 2860
 
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