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#11
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xyzzy wrote:
: What do you mean by a dog? Useful load, speed, what? What kind of TAS : do you get in cruise? I'd be curious to hear this kind of feedback from : 140 drivers, especially if they have also flown Warriors, 160s, or 180s : and can give comparative experience. Maybe I can help. I have a Cherokee 180 and have flown it 600+ hours. I have also ferried a Cherokee 140 with the 160HP upgrade back & forth from MA to FL a few times. I've also flown a Cherokee 140 with 150HP a couple times... Real world figures with 36 year old airframes (the Cherokees all have METCO wing tips, the Archer doesn't): My Cherokee 180, no speed mods, Piper wheel pants, trues out at 141 MPH at 70 ish % power. The 160 HP Cherokee 140, no speed mods, Piper wheel pants, trues out at 117 MPH at 70 ish %. It has the AMRD prop tip mod. The 150 HP Cherokee 140, no speed mods or wheel pants, trues out at 109 MPH at 70 ish %. An Archer 2 (Old style wheel pants) owned by my friend (we fly in formation) uses 50 less RPM to get the same TAS as I do. Climb: With 1 or 2 people and full fuel I rarely see less than 800 FPM initial climb in my airplane. I usually see more like 1200 FPM. With the cold weather, of course, climb performance is even better. In the summer at gross wt (2400 lbs) I'll see at least 500 FPM. The 150 HP Cherokee rarely makes 700 FPM, even in the winter. 500 FPM in the summer is also unusual. (This plane has a tired engine, though.) The 160 HP Cherokee is a solid 500+ FPM climb in the summer, 2 people and 36 gals of fuel. I haven't flown it in the dead of winter. Thoughts: The big triangular hole under the Cherokee 140 cowling for the cooling air exhaust is a tremendous source of drag. I would guess that the fiberglass cowling on my airplane is the source of most of the speed change between the 140 and the 180 airplanes. 20 extra HP just shouldn't change the speed that much. The 20 extra HP also shouldn't make that much difference in climb performance; I suspect that the much wider chord prop on the 180 makes a big difference at low speeds. The 180 prop pitch is also a climb prop pitch, and it can't be changed - it will easily make redline RPM at any altitude I've flown at. Both 140 aircraft have cruise props though I don't know the details. I'd be happy to arrange a demonstration if anyone's in the area. -- Aaron C. (N9376J) |
#12
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Aaron Coolidge wrote:
I'd be happy to arrange a demonstration if anyone's in the area. Where's "the area"? |
#13
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Tim Long wrote: Our 140 is coming up on 1600 hrs TBO. We really hate what a dog it is and would like more power. Planning ahead, we've thought of a few options: 1 - 160 hp conversion (this is almost the minimum we'd do) If you're already doing an overhaul, this is probably the most cost-effective option on your list. 2 - Powerflow exhaust (article in Plane and Pilot claims 20% power improvement - can it be combined with #1?) This one is good if your current exhaust system needs a lot of work and replacement parts. It's a bit pricey otherwise. The 140 owners I know that have installed it are very happy with its performance. 3 - 180 hp conversion Anybody know about praciticalities, costs of #3 above? I know it would require extra $$ for dissimilar engine exchange, STC costs, and cowling/engine mount mods. That's the biggie. I know two people who have done the conversion (was available from Avcon). It's popular out here in the mountainous west because the 140 is somewhat limited at high density altitudes found at mountain airports in the summer. Both of the owners were happy with the resulting performance, but both said that they'd never do it again. It was more expensive than they thought it would be (lots of mods required), it took months to complete, they had difficulty working with the current STC holders (not Avcon) and in the end, they still had a 140. John Galban=====N4BQ (PA28-180) |
#14
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Thoughts: The big triangular hole under the Cherokee 140 cowling for the cooling air exhaust is a tremendous source of drag. I would guess that the fiberglass cowling on my airplane is the source of most of the speed change between the 140 and the 180 airplanes. 20 extra HP just shouldn't change the speed that much. The 20 extra HP also shouldn't make that much difference in climb performance; I suspect that the much wider chord prop on the 180 makes a big difference at low speeds. The 180 prop pitch is also a climb prop pitch, and it can't be changed - it will easily make redline RPM at any altitude I've flown at. Both 140 aircraft have cruise props though I don't know the details. I'd be happy to arrange a demonstration if anyone's in the area. No demonstration, but I'd sure like to talk about those numbers. I purchased an older 180 ('63) about six months ago. She's great for her primary purpose -- traning. She can climb at ~1000 even in our San Antonio summers. Four people, temps in the low 90s this past late summer and she's still going up at 900FPM. So, I agree with that. I haven't had the opportunity to look up the exact type, but I strongly suspect a climb prop (not original -- changed in '92). That's based on performance. It climbs great compared to a 140 and a 140/160mod I've flown. But my speed is horrible compared to those numbers you quoted. At ~70% power, I'm lucky to get it to 110knots. The only way she ever gets into the yellow is decending with power still on!!! You mentioned the cowl with the big trangular hole in bottom -- well, that's what I've got. And to make it worse, there is a lip that stick downwards around the front of the opening -- creating even more drag. I also saw someone else mention a replacement cowl that improved airflow, dual exhaust (instead of muffler in front of the firewall), and less drag. Is that what you have on your 180??? Chuck N7398W |
#15
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Chuck wrote: I also saw someone else mention a replacement cowl that improved airflow, dual exhaust (instead of muffler in front of the firewall), and less drag. Is that what you have on your 180??? Chuck, Your -180 is one of the earliest examples ( a "B" model, I think). As such, it incorporated the same cowl and restrictive exhaust system that was used on the lower power models. Beginning with the "C" model in '65, the -180 cowl was changed to a two-piece fiberglass clamshell type and the less restrictive dual exhaust was added. With the old cowl and old exhaust (particularly the latter), I'm not surprised that you see a cruise of 110 kts. That's not unusual for the earlier models. I suppose that you could recowl the plane with a newer version, but you'd probably have to get some kind of official signoff for a mod like that (i.e 337 at minimum, field approval worst case). This could be pretty expensive for minimal returns and there might be issues fitting the existing exhaust into the newer style cowl. For the exhaust, Powerflow exhausts are available only for the early model -180s. It seems that the later model stock dual exhaust was not very restrictive and didn't warrant a specially modded pipe. If the -180 Powerflow improvements are similar to those of the -140 with a similar exhaust, this could improve your engine output significantly. Of course, the downside is that it's expensive. I'd probably wait until my exhaust system needed major work, then go with the Powerflow. John Galban=====N4BQ (PA28-180) |
#16
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Chuck wrote:
: At ~70% power, I'm lucky to get it to 110knots. The only way she ever : gets into the yellow is decending with power still on!!! Hmmm, my airplane cruises a needle width into the yellow arc at 70%. : You mentioned the cowl with the big trangular hole in bottom -- well, : that's what I've got. And to make it worse, there is a lip that stick : downwards around the front of the opening -- creating even more drag. That lip actually reduces drag quite a bit. I read a kitplanes article a while ago about cooling drag, and the "Cherokee 140" design is almost the worst except for that lip. Remove the lip, and the design is the worst possible. I wonder sometimes if Piper intended to make the airplane draggy to ensure that it didn't compete with the Comanche 180. : I also saw someone else mention a replacement cowl that improved : airflow, dual exhaust (instead of muffler in front of the firewall), : and less drag. Is that what you have on your 180??? Yes, the Cherokee 180 got the 2-piece fiberglass cown and a dual muffler design in 1965 IIRC (the Cherokee "C"). Mine is a 1968 Cherokee "D". (I think the Comanche 180 was dropped around 1965, as well, so the artificially high drag would no longer be required to limit speeds.) The cooling air outlet is lower than the rest of the fuselage, so the cooling airflow is to the rear and below the fuselage. The bottom of my cowling has no openings except a small hole for the nose gear leg, and a faired hole for the exhaust pipes. The nose gear leg hole is filled up behind the oleo strut with a sheel of aluminum. -- Aaron C. (N9376J) |
#17
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xyzzy wrote:
: Aaron Coolidge wrote: : I'd be happy to arrange a demonstration if anyone's in the area. : Where's "the area"? Southeastern Massachusetts. -- Aaron C. |
#18
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In article , xyzzy wrote:
One significant consideration is useful load. Do you just want the speed increase? There isn't any way to get a higher useful load. Interesting, my club has Warriors that have an STC raising the MGW to 2440 lbs. There isn't a similar STC for the 140? The highest max gross weight for a 140 is 2150lbs (some early 140's had/have a max gross of 1950 lbs iirc - those can go to 2150 lbs). -- Bob Noel looking for a sig the lawyers will like |
#19
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In article ,
Aaron Coolidge wrote: Real world figures with 36 year old airframes (the Cherokees all have METCO wing tips, the Archer doesn't): My Cherokee 180, no speed mods, Piper wheel pants, trues out at 141 MPH at 70 ish % power. The 160 HP Cherokee 140, no speed mods, Piper wheel pants, trues out at 117 MPH at 70 ish %. It has the AMRD prop tip mod. The 150 HP Cherokee 140, no speed mods or wheel pants, trues out at 109 MPH at 70 ish %. An Archer 2 (Old style wheel pants) owned by my friend (we fly in formation) uses 50 less RPM to get the same TAS as I do. I don't have speed mods, but do have those metcoair tips (or whatever the name is) Before I converted my 140 to 160hp, it could cruise at about 105 KTAS at ~4000' and 75% (with wheel pants) but I would usually plan on 100 KTAS. After converting to 160hp (and repitching the prop to a cruise prop) it'll do 110+ KTAS down low at 75% (without wheel pants). Climb: With 1 or 2 people and full fuel I rarely see less than 800 FPM initial climb in my airplane. I usually see more like 1200 FPM. With the cold weather, of course, climb performance is even better. In the summer at gross wt (2400 lbs) I'll see at least 500 FPM. The 150 HP Cherokee rarely makes 700 FPM, even in the winter. 500 FPM in the summer is also unusual. (This plane has a tired engine, though.) The 160 HP Cherokee is a solid 500+ FPM climb in the summer, 2 people and 36 gals of fuel. I haven't flown it in the dead of winter. before conversion: my 140 did not climb well, except in the winter. :-) However, unlike the 150hp 140 example above, mine would regularly climb at 1000fpm in the winter (initially). after conversion (even with the cruise prop), it's much stronger in climb. Easily 1000+ fpm climb even when pushing the nose over for cooling. In fact, I now have to worry about climbing into the KBOS Class B airspace when departing KBED to the west. I never had to worry had to worry about that before. -- Bob Noel looking for a sig the lawyers will like |
#20
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xyzzy posted the exciting message
: Tim Long wrote: Our 140 is coming up on 1600 hrs TBO. We really hate what a dog it is and would like more power. I fly warriors in a club and have been toying with the idea of buying a 140. I don't know if I'd be happy with less plane than I am flying now, but for 99% of the flying I do, a 140 would be sufficient, at least on paper. Hell, for 90% of the flying I do an Ercoupe or a Tripacer would be sufficient, but I'm not willing to go that small and limited since the 140 isn't THAT much more expensive to buy. What do you mean by a dog? Useful load, speed, what? What kind of TAS do you get in cruise? I'd be curious to hear this kind of feedback from 140 drivers, especially if they have also flown Warriors, 160s, or 180s and can give comparative experience. It's a dog even compared to a C172. The ceiling sucks and the climb rate sucks. If you get near gross it doesn't climb worth a damn. In the desert on a hot summer day we can't get much over 9000', and that doesn't buy a lot when you're trying to get to OSH or otherwise east of the Rockies. Try taking off from any runway when the density altitude is 4000' (not that high around here) or so - you need something like 4000' feet of runway if you're hot and heavy. It's a dog in that we want better performance for ceiling and takeoff distance. While speed and load carrying would be nice, they are not the biggest issue! Prime |
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