Bonanza Descent Planning and Engine Management Techniques

FlyWire takes a look at engine management during the descent. Of course fast is primary for us, so if you like to go slow just pull more manifold pressure/ RPM.
FlyWire is about exploring flight and the freedom this incredible experience brings us on a personal level. Flying has always captured the imagination and excitement of living life to its fullest. Hi, I'm Scott Perdue. In a former life I flew the F-4 and F-15E, more recently I retired from a major airline. I've written for several aviation magazines over the years, was a consultant for RAND, the USAF, Navy, NASA as well as few others, wrote a military thriller- 'Pale Moon Rising' (still on Kindle). But mostly I like flying, or teaching flying. Some of the most fun I had was with Tom Gresham on a TV show called 'Wings to Adventure". We flew lots of different airplanes all over the country. Now with FlyWire I want to showcase the fun in flying, share the joy and freedom of flight and explore the world with you. Make sure you subscribe if you want to go along for the ride!
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[@ronnl001]

View 1. Keep them coming scott!

[@rocket862]

I fly an A36 as well. I agree with the speeds and numbers you say. It seems when I am flying in the system it usually requires about a 700 fpm descent unless I pester the controllers. When this happens, I start peeling back power to about 18" slowly. I totally agree about staying at the top of the green on the descent. When I used to fly a 172 or my previous Piper Arrow I would push it into the yellow arc, but not with the A36. Love the VNAV function on the GTN 750, I keep a data field front and center at the top showing the required FPM. Anyway, love the videos! Keep em coming!

[@FlyWirescottperdue]

Thanks Rocket!

[@nickxidis9571]

My M20C yellow begins at 150mph so almost all descents are in the yellow as long as it’s smooth, 170-175mph typical. Just like the yours, starts with nose down trim and reduction in MP but not below 18”. We also have to bring in carb heat. Once we’re at altitude or bumps start nose comes up to slow to 120mph where we can throw out the gear. Flap speed is 100mph. I’ve set 90mph (flaps up) and 80mph (flaps down) as my minimum maneuvering speeds, so I never get slower than that in the pattern. 80mph on final. Before I go, I calculate an expected Vref based on weight (usually 60-75mph) that I try and hit over the numbers.

[@Parr4theCourse]

Nice job explaining everything !!

[@lostcreek163]

Keep engine/s hot, is the most important, had 8 520's that ran to 1800-2000 TBO, which is a hard row to hoe! Never over cool a piston engine on descent! Always let turbo cool for at least 5 mins. prior to shutdown. Save you a bunch of bucks. Best to all you Aviators!

[@charlestex8222]

Hi, Scott. Greetings from Brazil. I'd like to know how you manage the mixture control on descent, since the fuel/air ratio gets leaner and leaner as you lose altitude. For ex.: Do you enrich the mixture little by little as you descend, targeting 50ºF LOP or any other number? Or do you just leave it on cruise setting till pushing it to full rich for landing, on base or final? Keep on providing the great and reasonable content, as always.

[@FlyWirescottperdue]

I leave it at cruise lean until I need to go around.

[@charlestex8222]

@@FlyWirescottperdue Great. According to Mike Busch, you should gradually enrich it as you descend, but if you prefer to leave it cruise lean, he says that’s okay because the engine will start running rough, at some point, due to too lean a mixture, and then you’ll enrich it a little. Do you feel that’s true in reality? Have you experienced something like that? Or the engine actually gets leaner and leaner but never at risk of quitting? I’m curious cause sometimes academic data differ (a little) from real life. (I’m currently getting ready to fly a G36, hence the question). Thanks for you patience.

[@par5eagles975]

question- why not pull off RPM instead of MAP to slow your descent? or pull both in concert? Less fuel burn, greater prop efficiency, less noise.

[@FlyWirescottperdue]

I do that sometimes... mostly I like to go fast. I usually descend at yellow line. But that's just me.

[@nancychace8619]

Thanks for a nice video. Am curious what your cruising speed is? Been awhile for me - I'd have to dust off some cobwebs. Appreciate your sharing.

[@FlyWirescottperdue]

170 KTAS

[@5128goldenrod]

Also 4-500 FPM . I like to multiply The descent X( thousand feet) by 6....2 mins per x 3 miles per minute .

[@gorgly123]

When possible I like to use 300 ft./ minute decent rate. On a recent flight I was at 16,500 and started about 150 miles out (to 120 ft airport elevation)

[@thomasaltruda]

Jon Funanich that’s ok for VFR, but for IFR, they require a minimum of 500fpm or greater. I like to use 500fpm all the time, as the math is super easy.. For example, when at 8500 feet, if the airport is at 1000 feet, that’s 6500 feet to the TPA (Traffic Pattern Altitude). I would start a 500fpm descent when 13 to 14 minutes out. Then you can check your progress as you get closer.

[@stevegenzoli6158]

I fly my V35B decent pretty much the same way, Scott. Someone once told me to adjust my EGT on decent to 1300. Have you ever heard of that technique and do you see any value in that?

[@FlyWirescottperdue]

Steve- Not really. During the descent I'm more concerned with speed and CHTs. Since the descent doesn't put any stress from power production on the engine I can't really see it as important. I m not a 'total' believer in shock cooling... but I do try to manage thermal stress.