Spencer, you're saying the 421 was quieter than the 441.

Can you ballpark what that means?

Ex: From the cockpit I was able to speak to back passengers in a 421 using a slightly elevated voice level. Can you do that in a 441?

Thanks

Without a doubt, a 421 is quieter in cruise than any of the airplanes listed!

You don’t need a decibel meter to hear the difference!
As far as the engines, they get a bad rap (usually ham-fisted pilots or OWTs). The geared engines can be somewhat temperamental if not set-up right. Some will disagree but 5 years on 2 airplanes tell me different. I have to agree that the MX is pricey though. I find the cost of operation is more like $600+ an hour!
Good Luck in you investigation.

Any experience with Strakes on a 421?

Mike

Yes, I can’t tell any measurable difference!

That fits with my expectations. Anybody who claims a 4 knot speed increase is unable to truly measure it and hopes you aren't able to, either.

"Strakes on a plane".

Mike C.

Interesting. Speed mods are hard to measure and justify. I was more interested in the better ride quality and climb rate that the strakes claim. Bummer users are not convinced they are worth it.

I know in High end Audio guys can convince themsleves of all sorts of improvements that are not measurable. In that case the fact they think it's better is sometimes all that matters. With an Airplane mod you want actual data to support the added expense. But maybe guys that have them and feel like they are worth it are also right. We spend a lot on things to make us feel better.

Mike

I am going to install these at annual.

http://www.premiere-aviation.net/produc ... 4a-421c-3/

those are some mighty big claims they are making. Cant wait to get your report.

Hub caps do work. I flew a 1000 hours without them and 600 hours with them.

Max Nerheim did some more scientific comparisons with his strake and hubcap equipped 421. Here is his write up copied from one of his emails:


I installed Strakes on my 1980 421C, N2657N, during the annual this fall. Prior to installing the strakes the plane was always slower than book values both in climb and cruise. After the strakes it became marginally faster than book (from 0 to several knots faster), but the climb speed seemed to increase a lot with the strakes, even after I topped off with 270 Gallons! The largest noticeable performance increase was in climb and descent. Before, I used 25 inches and added flaps and gear to slow it down for landing. After strakes, and before I got used to them, I had to use speed-brakes on every landing to slow down. Shortly after the annual was completed, and before I had a chance to test the Strakes on a long high altitude flight, the Hubcaps arrived. The Hubcaps are made of fiberglass and have a slight curve to them like a large lid. I figure either to match the wing curvature or to make them stiffer. When the wheels are inside the wing on a 421C there is no door covering them up. The gear-door covers only the strut. The uneven and exposed wheel surface disrupts the air-flow over the bottom of the wing and cause significant drag. The Hubcap makes the wheels almost perfectly smooth and is supposed to reduce drag. Each Hubcap weights approximately 8 ounces. The 421 rims are made up of two halves, held together by many bolts. In order to mount the Hubcaps to the wheels without drilling holes in the rims, 3 brackets are supplied. The brackets attach to the bolts that hold the two rim-halves together. Mounting the brackets onto the rim is as easy as: jack up the plane, deflate the tire, remove one bolt-nut, slide the bracket on to the bolt, and retighten. The brackets fit snugly towards the inside curve of the rim, and no special bracket-alignment is necessary. Something I had needlessly worried about. After the brackets are in place, inflate the tire, mount the Hubcap to the brackets with three screws, and lower the airplane. The procedure takes less than 1 hour.

The first test flight was very impressive; the cruise climb and the cruise speed improved significantly. For example, in cruise I saw these numbers: 1800RPM, 29inches, 42 GPH ROP, 15500 feet, -7C, 30.03in barometric, 201KN TAS (POH is 195KN TAS). At lower power setting: 1700 RPM, 27inches, 29.5GPH ROP, 15500 feet, -7C, 30.03 barometric, 189KN TAS (POH is 179 KN TAS). During the last long flights with Strakes and Hubcaps I have experienced consistent cruise speeds above book values. At 25,000 feet at approximately 34 Gal/hour the cruise speed is now around 200 Knots, or around 220 Knots at 42-44 Gal/hour. Needless to say, getting 10 KTAS above POH numbers, when before I could not even get to book values is super awesome. I hope the added climb and cruise performance also means better single engine performance, which is what I am really after. Since I did not track performance after I installed the Strakes, I do not know how much of the performance increase is due to the Strakes, the Hubcaps, or both.

Since the subjective performance increase, based on my perception of previous airplane performance, seemed too good to be true (especially in climb), I went to Flightaware.com and used the historic flight data to calculate as objectively as possible average climb rates with and without Strakes and Hubcaps. Since there is no way of estimating the winds aloft accurately and since I do not remember the cruise speeds for each flight, I did not try and use flightawere.com to calculate average speed increases. I prefer 125 KIAS and 35in/1900 RPM for cruise climb (except for one flight from GJT to SDL where I used close to maximum power to 20,000 feet). Most of the flights with Strakes and Hubcaps were at gross weights, as were some of the prior flights without Strakes and Hubcaps. The flights without Strakes and Hubcaps were performed earlier in the fall, with the warmer air most likely accounting for some of the difference in performance. I have not been keeping accurate track of the GW on every flight. Hence the data as presented are my best estimate, with some error margin. When the climbs leveled off due to ATC restrictions, I removed this portion and the subsequent “jump” from the calculations. Hence, a climb to 20,000 feet can be based on two stable climb portions; one below the level-off and one after the level-off altitude. Based on my spreadsheet calculations, the average climb rate with Strakes and Hubcaps below 20,000 feet increased from 636 to 868 fpm, a 233 fpm (37%) improvement from the earlier flights without Strakes and Hubcaps. From 20,000 feet to 25,000 feet the average climb rate increased from 393 fpm to 648 fpm, a 255 fpm (65%) improvement from earlier flights without Strakes and Hubcaps.

Subjectively, the performance increase seems consistent with how the plane feels: the effort to get up to the middle flight-levels seem greatly reduced, and the plane is more stable in yaw (especially when heavy). It would be great if someone would test the single engine climb rate at gross with Strakes and Hubcaps. Could we expect a significant increase?



I called Peter Danto at Premier-Aviation.net (the maker of the Hubcaps) and asked if they could try and get an STC for increasing the GW with strakes and hubcaps since the climb performance has increased so much. Peter replied that it would be very hard to do due to FAA regulations requiring them to prove the strength of the airframe at the increased GW. I wonder, since the apparent performance (speed) increase with both Strakes and Hubcaps is about equal to 5% horsepower, or 2 inches of manifold pressure, would the performance increase imply the plane would be able to handle 5% more gross weight and perform the same as before Strakes and hubcaps were put on? In that case the GW increase would be approximately 378 lbs (17.8% increase in useful load). Given the cost of the modifications and the installation time, my opinion is that every 421C should have the Hubcaps (although I do not know how much this did by itself). If there is money left in the budget, I am super pleased with the combined performance of both Strakes and Hubcaps, and recommend both for speed and single engine safety margin. My expectations have been exceeded. The Strakes and Hubcaps allows getting up to the flight levels efficiently and fast, thereby saving gas, and thus increasing the range. My fuel burn rate in climb is almost twice as much as at 200 KTAS @FL250 in economy cruise (34GPH). Hence every minute in climb is 2 minutes I can spend at 200 KTAS. If increased speed is needed 220 KTAS can be achieved on just over 40 GPH around FL250, placing the 421C in similar performance category as some (smaller) twin turboprops! Another great benefit with piston engines was demonstrated during my flight to California last week; fighting strong headwinds I stayed at 8500 feet, had low fuel burn of around 40 GPH, and still enjoyed cruise speeds approaching the magical (my magical) 200 KTAS 

Disclaimer: The flight conditions were not exactly the same for the various flights. Nevertheless, I think that such a large increase in climb rates cannot be explained away only by different flight conditions. I have never seen these climb rates, or cruise speeds, from my 421C in the over 5 years I have owned and flown it.

Regards: Max

It evaporates long before it hits the ground.

I was curious enough to read all of that and was disappointed in the lack of data. No good data = no good conclusions.

If you’re really flight testing, or trying to, everything matters. OAT, IAS, ROC, GW, every engine parameter, etc. Just sayin’

421-probably best piston twin. Pricey--but best cabin.

I was curious enough to read all of that and was disappointed in the lack of data. No good data = no good conclusions.

If you’re really flight testing, or trying to, everything matters. OAT, IAS, ROC, GW, every engine parameter, etc. Just sayin’

This was missing from the previous email