Performance at rated ceiling

With a ceiling of 13800, per Van's specs, I'm wondering if the RV-12 would perform well over the Rockies. Do any of you guys have experience with this engine flying at those altitudes? The reason I ask is because one of the routes I would want to fly on a regular basis requires flying over mountain passes that approach that ceiling.

I just sold my plane to a guy who flew it back over the rockies and he had no issues whatsoever. It was a Highlander (not an RV-12) but it was the exact same engine. I live in Pennsylvania and he lives in Colorado.

A builder on VAF asked me to test the RV-12 at 12,500 MSL as he lives in CO, but is not done with his plane yet. At that altitude I could still climb at 200-400 FPM in my -12. Full fuel, one 200 pound (with clothes on) pilot. Flying over the big rocks should be no problem.

Also not RV-12 specific, but several CT owners I know report good operattions up through 13,000. Altitude-compensating carbs work fine. Cabin heat will be a problem as will cold oil and CHT temps.

TODR

I'm the -12 builder in Colo. that Larry was refering to. My -12 probably won't be finished until February or March, but I just sold a RANS S-7S, that I flew for 3 years here in Colo. That plane had the same Rotax 912, and it performed well up here. I once took it up to 14,500 just to see how it would do, and those altitude compensating carbs work beutifully. After I landed, I pulled a couple of spark plugs, to check the mixture, and it was spot on. Flying the passes, West of here, in the -12 should not be a problem. Steve

Vans pilots told me once that flying back and forth to Oshkosh they had a hard time getting it much over 13,000...is that high enough for the Rockies?

I believe that's high enough if you go though the passes - there are certainly peaks higher than that (I've ridden my bike up Mt. Evans and Pikes which are a bit over 14k). Perhaps the rockies crew should lobby for a 914 version

D/A

12,000' MSL in August is much different than 12,000' MSL in January.

Density Altitude is the critical altitude that needs to be understood here. On a hot August day with surface temps in the 85*F range, a field elevation of 5,000', the aircraft will act as if it is performing at around 8,000' on takeoff, which an approximate Density Altitude. Extrapolate that up to around 12,000' MSL and you begin to understand the problem flying at higher altitudes in the summer in low powered aircraft.

On the flip side, in January, same airport at 25*F, the DA will be around 3900' or so on the ground. So 13,000' + MSL altitudes may be possible.

Joe Blank said:

12,000' MSL in August is much different than 12,000' MSL in January.

Density Altitude is the critical altitude that needs to be understood here. On a hot August day with surface temps in the 85*F range, a field elevation of 5,000', the aircraft will act as if it is performing at around 8,000' on takeoff, which an approximate Density Altitude. Extrapolate that up to around 12,000' MSL and you begin to understand the problem flying at higher altitudes in the summer in low powered aircraft.

On the flip side, in January, same airport at 25*F, the DA will be around 3900' or so on the ground. So 13,000' + MSL altitudes may be possible.

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Good point. Our 912S has run fine at DA above 12,000'. Highest we've seen is 9999 MSL and about 65F (we don't have an OAT, all steam gauges). The Rotax ran fine, no problems. At low DAs (temps below ISA), we can get well into the yellow at WOT and level flight (125kt). No, we don't exceed 120Kt at SL under ISA conditions.

Most LSA are rather overpowered (compared to non RVs) and tend to climb well even at high DA - provided that the prop is pitched correctly! The 100Hp Rotax and 1,320 lb MGTW limit makes for good power loading. We typically see 400-500 fpm in a 85-90kt cruise-climb out of BZN on a warm day (85F) and nearly MGTW - DA is nearly 7500 at the field. Any "conventional" RV will do better, sure, but that's not what the -12 is about.

None of the Rotax powered LSA that I've flown had me feeling that they were lacking in climb performance. More is always better, I know, but I haven't had to alter my flight path because we weren't climbing fast enough. Cooling can be an issue in some aircraft, forcing more of a cruise-climb, but from what I understand, the -12 has good cooling characteristics.

TODR

Getting through the Rockies

I've never flown east of Nevada, but hope to go to Oskosh next year. What route, or routes can be flown at the lowest altitudes through the Rockies? I've flown in and around the Sierra Nevada mountains for years in a 151 Warrior, and am familiar with high density altitudes. I'm just curious about the best way to get through the Rockies. I'm based near San Francisco.

Mark Henderson said:

I've never flown east of Nevada, but hope to go to Oskosh next year. What route, or routes can be flown at the lowest altitudes through the Rockies? I've flown in and around the Sierra Nevada mountains for years in a 151 Warrior, and am familiar with high density altitudes. I'm just curious about the best way to get through the Rockies. I'm based near San Francisco.

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Mark,

On June 12, 2002, I flew my Cherokee 140 (150HP) from San Carlos, CA (KSQL, just South of San Francisco, as you know) to Truckee-Tahoe (KTRK), then to Battle Mountain, NV (KBAM), then to Fort Bridger, WY (KFBR). It was a long day, but Truckee and Lake Tahoe were beautiful! From WY it was all downhill to Minnesota. The elevation at KTRK is 5900 feet, but it is in a bowl, so we had to circle several times to clear the mountains on departure. (My plane's climb rate in June at near max weight was less than 500 feet per minute.)

The flight was part of my IFR cross-country training, so I had my CFII in the right seat. Very fortunate for me, because she had been flying in the mountains at least 4 years at Embry-Riddle in Prescott, AZ.

I don't know how this route compares to others.

Don