Alphabet Challenge Leg 31 K49X - KL52

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Talan2000
Posts: 207
Joined: Mon Dec 15, 2014 8:59 pm
Location: McKinney, Texas, USA, Earth

Alphabet Challenge Leg 31 K49X - KL52

Post by Talan2000 »

Pilots,

After a quick pit stop at Chemehuevi Valley -- The airport that appears the most often in the challenge I believe...I love trying to say that right - went so far as to read up on the Native American tribe and a snapshot of its history ... it's back to the coast.

http://peaware.pilotedge.net/flight.cfm?id=88602

I don't know about you, but I'm beginning to think of this strip near PMD where desert meets mountain as my local neighborhood after criss-crossing it so many times. And I look over at Apple Valley and the Logistics airport with fond I-rating memories...can I see anyone arcing? Nope, not today...

Lessons Learned:
The challenge you face in this flight is managing your descent from the mountains down to the sea. Maintain a nice cushion but don't get stuck too high. Flying Drill brings up a really magnificent point about shock cooling your engine by descending too rapidly. This is an issue for Pistons, but not really turboprops, but if anyone is flying that Baron don't follow any of my descent profiles or you will be in for a shock...

Oceano is another nice little airport I'd kinda like to see in the real world. I love to read the A/FD details (I can imagine the locals, justifiably, coming after me with pitchforks if I made too much noise coming in to their sleepy coastal hamlet...) Oh, the strip is a bit shortish so don't be long or fast...
Ahhhh
Ahhhh
Oceano.JPG (27.21 KiB) Viewed 5046 times
Knowing I would be high and that I have a hard time seeing "new" airports I planned to overfly the field and head out to sea (note the right traffic) upon arrival. Your choice, there's no info.

My heart skipped a beat on this one because after landing I was caught in an odd loop where PEaware didn't show me as having completed the flight - though I never logged off. I filed the next leg about 4 times but it always had my old segment. Finally I flew a lap in the pattern and landed again. That did the trick, not sure why it thought I had logged off. If it happens to you. Log off. Then log on and "refly" that arrival...I had a sim crash (later on) that I was able to salvage this way - whereas before I REFLEW the entire flight. No thanks.
Keith Smith
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Re: Alphabet Challenge Leg 31 K49X - KL52

Post by Keith Smith »

Shock cooling is not widely accepted as gospel in pistons.

2 things about it:
1) when you switch your engine off after a flight, the rate of cooling that is realized is probably far greater than what happens in the air when you pull power, and
2) if you run lean of peak in a piston, you can always enrichen the mixture, bringing it closer to peak, or even slightly rich of peak to maintain the CHT's. I do this in my airplane as an experiment more than anything else and am able to RAISE the CHT's in the descent if I want, even though I'm going 30kts faster in the descent.

By and large, you also don't need to pull power before descending in a piston airplane, not until you're down to and altitude where wide open throttle is going to produce 75% power or more, at which point you are going to want to pull power or stop the lean of peak operations.
wmburns
Posts: 474
Joined: Mon Jun 10, 2013 7:28 am

Re: Alphabet Challenge Leg 31 K49X - KL52

Post by wmburns »

I may have some interesting things to add as well as some questions. I mainly fly the X-Plane Carenado Barron 58. In this version the cowl flaps work. I have observed that if it hot outside and you forget to open the cowl flaps the CHT's will run hot as should be expected. Also observed that if during higher altitude cruising that if you forget to close the cowl flaps the CHT's can drop out of the green area. I have seen the oil temperature out of the green as well. Closing the cowl flaps gets the temperature into the green most of the time.

I have cruised at 9,000+ in economy cruise on a cold day (cowls closed) and had noticed the CHT running right on the lower edge of the green range. On the Barron 58 economy cruise is defined as, 21" manifold, 2100 prop RPM, and CHT 20 degrees lean of peak (LOP).

The real Barron 58's POH recommends performing descent at no more than 170 IAS. I can't descend without exceeding 170 IAS without a power reduction with a slight enrichment of the mixture. Obviously one of the reason for enriching the mixture is to prevent the motor from "leaning out" during the descent. It does also increase the CHT's. Even following all of these recommendations during a long descent the CHT's won't always remain in the green.

I also try to maintain a 3% rate of descent. The rule of thumb is to take IAS / 2 *10 and use that as the FPM rate of descent. At 170 IAS this make the ROD to be around 850. However I have found myself too high on many occasion even using a ROD of 1,000FPM. This is an area that I wanted to do some research on to see if my planning skills could be improved.

All of this had me wondering about what action should a pilot take if during descent the CHT's drop too low? Is it enough to monitor CHT and set mixture to peak EGT? Or when it's time to re-apply power should it be done slower to allow the motor time to heat up?

Regarding how an air cooled motor cools on the ground verses in the air. I understand the logic that it's similar. But..... In the air the environment differs:
  • The motor has wind of the prop and the plane's motion passing over the cowls,
  • The outside air is cooler to begin with.
  • The motor is generating more heat because it's running and working.
  • When the motor is shut down on the ground, it isn't likely to be restarted and asked to work hard. IE, it will cool naturally back down to ambient temperature and remain off.
Note, I know the behavior seen is mostly dependent upon the modeling in the Carenado BE58. IMO the Carenado's modeling is much better than the default Barron. I also realize that my experiences are with a simulation and not a RW plane. My intent is just trying to learn what's reasonable and what's not. As well as to learn how best the manage the systems on the BE58.

Thanks for the input.
flyingdrill
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Re: Alphabet Challenge Leg 31 K49X - KL52

Post by flyingdrill »

VFR in X-Plane's Baron - which I hardly ever fly. After checking with Center that the MOAs were cold, I was out of 49X, doglegging around the high stuff, then climbing to 10,500' to HEC. After HEC, I asked Center whether I could enter R2515, and received an unsurprising "No!" So, I went West, South of the Border (not "down Mexico Way" for the Sinatra fans), and direct to FLW after passing Rosamond Lake. A little later, I started a slow descent to 6500' to try and get the advantage of a healthy tail wind component I'd been led to expect from my weather report. I didn't see much effect on the GS, and this was confirmed by the weather in the FLW area, where the tail wind component had indeed disappeared. Can't win. Further slowish descent to around 3000'. Dropped off flight following with Santa Barbara approach, and made for L52, which I always find very difficult to make out in my X-Plane installation (I do have someone's L52 scenery). The gray runways and taxiways blend into the surrounding vegetation, and I find pattern work there hard, because I lose the field at low altitudes. I went around at the first attempt. I put the runway heading in the Garmin 530 OBS setting, which gave me a line to go for, and got down on the next try.

Keith's comments on shock cooling are fair. Is it a myth? Is it one of those contentious things pilots discuss endlessly - like "rich or lean of peak", etc.?

You have probably cooled the engine when shutting down, as you have reduced power on approach and in the flare, and then almost idled it in taxiing, which could be quite a while!
I was warned of shock cooling by numerous instructors. Rotax engines were not to be prone, because they have water cooled cylinder heads. PA28 and C172 POHs do not mention it. There is a cautionary paragraph in the DA-40-180 POH. Beech's Baron POH admonishes you to monitor temperatures very carefully in cold weather descents, as the engines can overcool- well, that's what it says.........

See this article: http://www.avweb.com/news/maint/182883-1.html
Peter Grey
Posts: 5716
Joined: Tue Oct 12, 2010 3:21 pm

Re: Alphabet Challenge Leg 31 K49X - KL52

Post by Peter Grey »

Keith's comments on shock cooling are fair. Is it a myth? Is it one of those contentious things pilots discuss endlessly - like "rich or lean of peak", etc.?
Yes shock cooling is one of those endless debates.

My argument, do what the book says, if you want to be really cautious keep the CHT in the green as appropriate, beyond that I have no comments on the area.
Peter Grey
PilotEdge Director of Quality Assurance and Operations
peter@pilotedge.net
Keith Smith
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Re: Alphabet Challenge Leg 31 K49X - KL52

Post by Keith Smith »

wmburns, IAS translates to vastly different TAS depending on altitude and temperature, so I wouldn't attempt to use any formula that plans a rate of descent based on strictly on IAS. I tend to work the other way, start with a known rate of descent that is comfortable and won't exceed whatever speed limit you want to use (for my plane, that's top of the green arc unless I am highly confident of a smooth ride all the way down to the deck). Let's use 500fpm as a starting point. That's 2 minutes for every 1000ft. If you need to get from 10,000ft down to the surface, that's a 20 minute descent. If you want to equate that to a distance, feel free, but if I'm using GPS, I'll simply wait until my ETA is approaching 20 minutes, then start down. Bear in mind, you'll pick up speed in the descent (at least initially, while you're still high), so you just need to monitor your progress on the way down.

What I actually do in my plane is use the VNAV function and plan for a 400fpm descent profile. Once the VSR (vertical speed required) hits 400, I start a 500fpm descent. This tends to account for the higher groundspeed during the descent.
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