BAC Fest, Power Flow, AECI Summaries

Rellihan

Rellihan

Touring the Galaxy
It would be greatly appreciated if some of the BAC Fest attendees, and particularly those who flew in the PFS Sundowner, could weigh in with an article (as a post under this Topic). Our non-attendees would love to see more feedback on the show as a whole; on the results of the PFS video presentation and flights; and on the impressions left about the AECI parts (current gear cushions and Hartwell-style handle, and proposed parts).

While I can ask PFS, I seriously doubt that Robin would be willing to give us a copy of the video for download on the website. There is too much proprietary information there, for the as-yet non-STC'd and non-patented parts.

As noted in the talking points following the Friday night Dinner, BAC is pursuing a PMA on the yoke shaft bushing. Bill Manhein has completed the drawing. What I need now is a bad bushing, which can be destroyed for material analysis. Please let me know if you have one you can send me. I could also use a couple of bad/repairable door braces, if anyone has one or more to spare.
 
Mike,

I have a new bushing. I'll check to see if I have an old bushing. You are talking about the bushing that the control wheel lock goes into? Let me know.

Mike Hippensteel
 
Power Flow Test Flight

I was one of, I think, three of us who got to fly the Sundowner with the Power Flow system. Quite frankly, I was impressed.

I am not too sure on the wheelpants, and I will mention them at the end here, but the Power Flow tuned exhaust is a winner. Below are the specs from my less than rigidly calibrated flight:

TAKE OFF/CLIMB:
Two of us on board; 30-35 gallons of fuel.
Field elevation: 1408'
Air Temp: 100' (Believe me!!)
Developed 2700 RPM on the take off roll! (We almost never see more than 2500 with ours)
Climb out at 105 MPH
Rate of Climb: 750-800 FPM (At a Density Altitude of 4500' !!)

CRUISE:
Level flight, 4500' MSL
OAT=89'
Tach=2650 RPM - 138 MPH IAS!
Tach=2790 RPM (Firewalled, leaned) - 145 MPH

The jury is still out on the wheel pants. I am not convinced that they provide more than a couple knots (and Robin Thomas, the designer, isn't happy with them yet either.). For sure they are not nearly as ugly as I thought the might be; but they do look strange. She handled like any other Sundowner. Until the pattern. If there is one thing our planes excel at, it is slowing down when you pull the power. This bird just did not want to slow down to Flap speed! A mile out we pulled power to 1900 RPM and still had to put significant back pressure on the yoke to get below 100 MPH.
When we got to Vf, Jeff, the test pilot in the right seat, who was required to make the landing, yanks the Johnson bar to full flaps. So I could not tell if the effect follows all the way down the line.

But I am working toward replacing our two year old exhaust with the Power Flow.
Steve Cote
N1958L
 
Yes, Mike H; the Nylon bushing for the control yoke shaft; I need a bad one that can be destroyed.

Steve C, thanks very much for the PFS report; I hope that the other two folks will make a report as well. I have since learned (from Dave Buttram) that PFS may make the presentation download available to BAC members via a link to a section of the PFS website. They are reportedly working on it.

I sure am happy to see those RPM numbers. I have been speculating that the recovered HP and reduced drag would enable the 'over-pitched' prop to 'come into its own' on the fixed-gear planes. It sure looks like it is, on the demo plane. That means it will make a lot more sense to get the PFS parts and take advantage of the prop as it is, rather than trying to get the pitch reduced.

Unless I did the math wrong (no TAS calculator here at the house!), I'm coming up with 150 MPH and 158 MPH respectively for TAS numbers. If all of the reported numbers are correct, the PFS Sundowner is achieving Sierra speeds, though undoubtedly burning more than my 9 GPH to do it. The combination of results (RPM numbers, ROC numbers, IAS and TAS numbers, and reluctance to decelerate) tells me that both the exhaust and wheel pants are contributing to the results. That means you can save gas when you want to, or go faster when you want to.

Note that the reluctance to decelerate should be a key sign of reduced drag; which in turn, should mean that the wheel pants are helping. When I went through some minor drag reduction efforts on my Sierra, that was the first solid indication of some success. When I nosed Sunny B over for a moderate descent (200-300 FPM), he accelerated about ten knots faster than he used to, at the same cruise power setting.

FWIW, I also believe that the raked exhaust on the PFS system is both reducing exhaust stack drag while adding some residual exhaust thrust (the old front hole was capped off). Our stock exhausts are about as bad as they can be; round tubes, sticking straight out, right up close to the prop. I have read that a 2.5" round tube that is 12" long, perpendicular to the airstream, has as much drag as several running feet of wing.

Hint- if you ever get the chance, swap your old round-tube boarding steps for the newer steps, which are made from the semi-streamline tubing. I can't get by without them altogether, but some of you probably can. I have been toying with the idea of shortening and narrowing a used set, then seeing how much difference they make. Haven't yet made it to that project. Old-time Bonanza gurus swear that the switch from retractable to fixed step (there is only one) cost the Bonanzas several knots.
 
I flew the PowerFlow Sundowner on Friday afternoon and will try to give the numbers as I remember them. It was hot Friday, too. Just over 100F! We had three aboard, and I would guess our total weight at a bit over 600lbs. I think we had about half tanks of fuel or around 180lbs.

Climb at 100 mph was around 300-400 fpm until we got up a few hundred feet and then increased to around 500-600 fpm. We leveled off at 3500 feet MSL and I saw about 130 mph indicated at 2500 rpm as set using the electronic tach. The panel mechanical tach read a bit over 100 rpm high. At wide open throttle, I saw 2650 rpm and 135 mph indicated. My sundowner gives about 105 - 110 mph indicated under these conditions.

Handling was pure Sundowner - couldn't tell we had wheel pants on, though the rigging seemed to be a bit off. I needed lots of rudder in right turns and almost none in left turns. I tried some semi-steep turns, 45 degree bank or so, and it handled great.

I sat next to Robin at dinner Wednesday evening and he told me the last modification he made to the pants to fix one problem caused a problem elsewhere (the tuffting problem seen in the video), and he feels the pants are only giving a three mph increase in the current configuration.

I was quite happy with the results overall, but there are some things to consider. They are running a newly-overhauled engine, and I'm used to on that has 1500 hours on it. On the other hand, the current exhaust is tuned for peak performance at 2350 rpm and they are going to modify it for peak performance at 2450 rpm, which should help even more.

They had hoped to be able to fly with and without the Powerflow exhaust, but didn't feel they had the time to switch back and forth. That would really have shown the performance difference.

I am anxoiusly waiting for the official results!

I can't remember the name of the person in the back seat, but I hope he responds with his impressions as well. My memory is less than perfect!
 
Mike memtioned the 'over-pitched prop' I remember he more fully exlained what he ment by this in a previous post. I wanted to reread this but could not find it using the search. It was a very good discussion that in light of the PFS I would like to see again. maybe with even more detail.

Mike Dawson
 
If you do a BAC search on 'prop pitch' and read the first yellow-highlighted FAQ, you'll get an education on the subject itself. If you then do a search on 'prop re-pitching' and read the Forum Topic string, you'll get most of the rest of what you are looking for. I considered putting links to the FAQ here instead, but the link takes you to the entire page of FAQs, not the specific one you want.

Anyone considering having their prop pitch reduced needs to be sure that they won't want the PFS exhaust and wheelpants instead. Otherwise they will wind up having to have the pitch put back in, or wind up throttling back in cruise to avoid exceeding red-line. There is a 'twist allowance' in every new prop. It is used up during repairs and re-pitching. Once reached, that specific prop can no longer have the pitch adjusted (for repairs, overhauls, or re-pitching).
 
It was a great trip. I enjoyed every moment of it.

And I want to thank those who encouraged us and enabled it, such as Mike Rellihan and Dave Buttram, and those brave souls who rode with us!

Meeting the BAC people was a privilege, and I was much impressed with the high standard of intelligence and knowledge.

Our trip back was incredible… we did not leave until after 2 pm, and arrived back in Daytona Beach at about two and a half hours after midnight. I had not done any night flying in a very long time, and it was beautiful, especially as the Sundowner was purring like a kitten.

In response toy Mike Rellihan’s suggestion, we are preparing a lot of information to go on our www.
Speedpants.com website. It will be posted within the week. I hope to update it from time to time to let you know of our progress.

We had an unexpected extra rider on Saturday morning, called Mark Hokeness, a VP at Beechcraft. He had just landed from a flight with a student in a Sundowner, and was looking over ours with interest. After landing, I heard him say that he was very impressed, and that N23HK was a solid 15 knots faster than any other Sundowner he had flown… He had been flying the Premier the day before, and later in the day we saw him taking off in a Stearman at Benton Airpark! Mark must really love to fly!

We still have a long way to go before I am satisfied, but your encouragement sure helps to keep me on track.

Regards,

Robin
 
rgschmi said:
Handling was pure Sundowner - couldn't tell we had wheel pants on, though the rigging seemed to be a bit off. I needed lots of rudder in right turns and almost none in left turns. I tried some semi-steep turns, 45 degree bank or so, and it handled great.

I can't remember the name of the person in the back seat, but I hope he responds with his impressions as well. My memory is less than perfect!
Click to expand...

Bob,
That was Bob Grauer in the back.
And, yes, there was something funky with the rudder and/or pedals. We noticed it on taxi...took a lot of right rudder to stay straight or turn right. I mentioned to Jeff that they should check the centering cable and the rudder/aileron interconnect. He looked thoughtful, perhaps something not attended to, as is often the case in the Mouse.
 
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