Piston twin for the mountains: Do they exist?

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Alexb2000

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Alexb2000
Does a REAL mountain twin exist? By REAL I mean lose one on takeoff at gross and meet TERPS requirements on an OEI departure from a mountain airport. I've always thought a Colemill 550 B55 Baron turbo normalized would be the ultimate mountain twin, if only they existed. Fantasy aside, does anyone know of a piston twin that will do it?
 
The best you could do would be a RAM T310R with the 335 HP intercooled engines. My friend has one, and it performs as well if not better than the Cheyenne II.

Baron 56TC might do it, too. Or a 310 Riley Rocket.

When I was down visiting GAMI a few years back, they had a 55 Baron they were putting turbo-normalized 550s on. Might do it, but still only be 600 HP total. I think the 56TC or 310 options are your best bet.

I wanted to put GTSIO-520s on our 310. That wouldve done it no question.
 
Ted DuPuis said:
The best you could do would be a RAM T310R with the 335 HP intercooled engines. My friend has one, and it performs as well if not better than the Cheyenne II.

Baron 56TC might do it, too. Or a 310 Riley Rocket.

When I was down visiting GAMI a few years back, they had a 55 Baron they were putting turbo-normalized 550s on. Might do it, but still only be 600 HP total. I think the 56TC or 310 options are your best bet.

I wanted to put GTSIO-520s on our 310. That wouldve done it no question.
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I almost forgot about a couple of those. 56TC a monster for sure, super duper crazy fuel burn.

What are your thoughts about the engines on the T310R?

Would a Riley rocket really be able to handle the mountains? No T/C's right?

The boys in Ada have been rumored to be coming out with a TN Baron for a looong time. I think they are working on the fuel replacement more than anything now.
 
Alexb2000 said:
Does a REAL mountain twin exist? By REAL I mean lose one on takeoff at gross and meet TERPS requirements on an OEI departure from a mountain airport. I've always thought a Colemill 550 B55 Baron turbo normalized would be the ultimate mountain twin, if only they existed. Fantasy aside, does anyone know of a piston twin that will do it?
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At gross weight, the SE performance of almost any piston twin, turbo'd or not is marginal to non-existent above 6000-8000 DA and AFaIK even turboprops have DA limitations for hot/high takeoff at MGW. I haven't personally verified it but my B55 with oversized engines is supposed to have a SE service ceiling at MGW in excess of 10,000 and an acceptable (e.g. >200 FPM) SE climb rate at 6000 DA. But 200 FPM at 100 KTAS (Vyse) is only 120 ft/nm which is way less than the gradient required for many if not most DPs from mountain airports. Reducing the gross weight pays big benefits WRT SE climb performance though, and that's the way I try to operate from high runways.
 
gismo said:
At gross weight, the SE performance of almost any piston twin, turbo'd or not is marginal to non-existent above 6000-8000 DA and AFaIK even turboprops have DA limitations for hot/high takeoff at MGW. I haven't personally verified it but my B55 with oversized engines is supposed to have a SE service ceiling at MGW in excess of 10,000 and an acceptable (e.g. >200 FPM) SE climb rate at 6000 DA. But 200 FPM at 100 KTAS (Vyse) is only 120 ft/nm which is way less than the gradient required for many if not most DPs from mountain airports. Reducing the gross weight pays big benefits WRT SE climb performance though, and that's the way I try to operate from high runways.
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Lance-

That's the problem, I carry a lot of people and stuff. It wouldn't make sense in my world to have to fly light weight.

The performance of the B55 with 550's is amazing NA. Your numbers are about what I was thinking, just won't quite get there on a DP.

Do you have 470's?
 
Alexb2000 said:
I almost forgot about a couple of those. 56TC a monster for sure, super duper crazy fuel burn.

What are your thoughts about the engines on the T310R?

Would a Riley rocket really be able to handle the mountains? No T/C's right?

The boys in Ada have been rumored to be coming out with a TN Baron for a looong time. I think they are working on the fuel replacement more than anything now.
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56TCs don't have to have crazy fuel burn. The 541s will run just fine at a lower power setting, and will probably last longer that way. Since the 56TC is a 55 Baron body, no reason you couldn't get 180 kts on 30 GPH or less.

The RAM T310R engines make an insane amount of power. When I flew my friend's plane it truly performed equal or better to the Cheyenne. He specifically went for that conversion based on OEI performance, and got everything he was looking for. He has about 600 SMOH running the engines hard but rich, and has had no problems. 1600 TBO. The ECI cylinders supposedly have cracking issues with those RAM conversions, but I think CHT plays a big factor. He runs about 320F burning 44 GPH combined and 230 KTAS @ FL190. Pull back to an economy cruise and I'd bet 30 GPH for 185 kts at a lower altitude.

The Riley conversion I'm thinking of (maybe the Turbostream?) had Navajo engines in a small body 310. I've seen different numbers - 310 HP to 350 HP, but all turbocharged. I'd expect similar performance to the RAM.

I'd agree not to expect anything from Ada soon. And if they do make it, it'll be expensive. Although RAM charges $180k for the above mentioned conversion, but that includes engines, props, intercoolers, etc.
 
Ted DuPuis said:
56TCs don't have to have crazy fuel burn. The 541s will run just fine at a lower power setting, and will probably last longer that way. Since the 56TC is a 55 Baron body, no reason you couldn't get 180 kts on 30 GPH or less.

The RAM T310R engines make an insane amount of power. When I flew my friend's plane it truly performed equal or better to the Cheyenne. He specifically went for that conversion based on OEI performance, and got everything he was looking for. He has about 600 SMOH running the engines hard but rich, and has had no problems. 1600 TBO. The ECI cylinders supposedly have cracking issues with those RAM conversions, but I think CHT plays a big factor. He runs about 320F burning 44 GPH combined and 230 KTAS @ FL190. Pull back to an economy cruise and I'd bet 30 GPH for 185 kts at a lower altitude.

The Riley conversion I'm thinking of (maybe the Turbostream?) had Navajo engines in a small body 310. I've seen different numbers - 310 HP to 350 HP, but all turbocharged. I'd expect similar performance to the RAM.

I'd agree not to expect anything from Ada soon. And if they do make it, it'll be expensive. Although RAM charges $180k for the above mentioned conversion, but that includes engines, props, intercoolers, etc.
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Ideally it would be nice to find a twin that could be pulled back to the mid-20's at ~180 Knots. Yet, have the power if needed. Maybe that's just asking too much.

I guess I was mis-informed about the 56TC, I thought they were a 35-40 GPH bird.

I'll have to do some homework on the RAM T310R. Sounds like you're confident it will do it.

Appreciate the responses.
 
Ron Levy said:
How big a payload do you want to haul?
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No fuel payload of 800 minimum, 1000 would be better. At least 700NM range with generous IFR reserves hauling those weights. I'm not a big stickler for speed with $6 gas, 180 would be fine in economy cruise.
 
Turbocharging is a must at mountain airports, but there are also published alternate IFR departure procedures for places like Aspen and Reno that are readily available that take most of the OEI performance headaches away. These procedures are used by the 121 and many 135 and 91 operators in places like Aspen. In effect, Aspen becomes just another airport. It's called runway analysis and is offered by many vendors.
 
LOP you could probably do mid 20s on fuel and 180, especially up high. Turbo birds will lose some engine efficiency, but gain some of that back with altitude.

The 56TC is any other high-power engine. You can run it at 35-40 GPH. You can also pull it back and save some fuel. I think most people who buy the high power birds say "I didn't buy this to go slow" and plan accordingly. I tend to think like you in terms of wanting a balanced approach on speed vs economy but want the OEI performance. Our 310 with 520s works well for that, although not as well as the T310R.

I think you'd be happy with it or a 56TC performance wise. Keep in mind that in a real situation like that, it still won't be fun. And the other question is how close to gross you intend to run.
 
Alexb2000 said:
No fuel payload of 800 minimum, 1000 would be better. At least 700NM range with generous IFR reserves hauling those weights. I'm not a big stickler for speed with $6 gas, 180 would be fine in economy cruise.
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Now that might get a bit harder to hit for 700 nm and generous reserves.
 
Alexb2000 said:
Ideally it would be nice to find a twin that could be pulled back to the mid-20's at ~180 Knots. Yet, have the power if needed. Maybe that's just asking too much.

I guess I was mis-informed about the 56TC, I thought they were a 35-40 GPH bird.

I'll have to do some homework on the RAM T310R. Sounds like you're confident it will do it.

Appreciate the responses.
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I've got several hundred hours in 56TCs and they are great birds. They are also 40 to 45 gph birds and below 10,000' they are aren't much faster than a B55. They come into their own at oxygen altitudes. Large engines powered back are never as efficient as smaller engines operated at more efficient power settings.
 
Dead Stick said:
I've got several hundred hours in 56TCs and they are great birds. They are also 40 to 45 gph birds and below 10,000' they are aren't much faster than a B55. They come into their own at oxygen altitudes. Large engines powered back are never as efficient as smaller engines operated at more efficient power settings.
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What power setting were you operating the engines at?
 
Ted DuPuis said:
Now that might get a bit harder to hit for 700 nm and generous reserves.
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Mountain reserves would be a better description. Take four (meat eating per the other thread) adults to the mountains with a bunch of ski gear and 10 different pairs of Ugg's per woman and the weight gets up there. I figure 200lb per person all in as an absolute minimum.

The problem with reserves is the nearest sensible alternate in the mountains could be 60+ miles with a climb to the high teens required. That plus another 45 ends up being a lot of gas onboard.
 
Alexb2000 said:
Mountain reserves would be a better description. Take four (meat eating per the other thread) adults to the mountains with a bunch of ski gear and 10 different pairs of Ugg's per woman and the weight gets up there. I figure 200lb per person all in as an absolute minimum.

The problem with reserves is the nearest sensible alternate in the mountains could be 60+ miles with a climb to the high teens required. That plus another 45 ends up being a lot of gas onboard.
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This is probably a good part of why most folks go to turbines. You can get the fuel numbers - the R can be had with over 200 gallons if truly maxed out - one guy had about 230 gallons for his. But then you and your wife will hit gross. If you take your friends along, you'll be over gross, and there goes your OEI performance, not to mention legality.

I hear Wayne can put you in a G-V for 27 mil. That should do it. :)
 
Ted DuPuis said:
What power setting were you operating the engines at?
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75% but, like I said, even at that power setting they weren't any faster the a B55 down low. The airplane was a hoot to fly, but there was no real advantage to it until you went up above 10000'. I'm sure those stubby little 3-bladed props had something to do with that.

Like I said earlier, the key to operating out of mountain airports is to take a page out of the 121 and savvy 91 & 135 operator's handbook and educate yourself on Alternate Departure Procedures. All of a sudden the nearly impossible climb gradient requirements pretty much go away at no loss of safety. You've got to pay for them, but they're readily available.
 
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Dead Stick said:
75% but, like I said, even at that power setting they weren't any faster the a B55 down low. The airplane was a hoot to fly, but there was no real advantage to it until you went up above 10000'. I'm sure those stubby little 3-bladed props had something to do with that.
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I'd expect your numbers for 75% power and down low. The props aren't very efficient (2900 RPM makes them small), and the airframe hits a wall. So, no surprise. Down to 55% or 65% power you'd likely lose minimal speed and get significantly improved fuel burn. Since Alex is talking about wanting OEI performance and doesn't mind pulling back a bit, it would still make sense. We pull back on the 310 and save a good bit of fuel for it. I could get the Navajo back down to the mid-20s LOP doing maybe 160-170, but we never did that except on ferry flights - owner being in a hurry and all.

Like I said earlier, the key to operating out of mountain airports is to take a page out of the 121 and savvy 91 & 135 operator's handbook and educate yourself on Alternate Departure Procedures. All of a sudden the nearly impossible climb gradient requirements pretty much go away at no loss of safety. You've got to pay for them, but they're readily available.
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That's good information and I'll be looking for that if I start going to the mountains. But, more climb rate can only help. :)
 
Ted DuPuis said:
That's good information and I'll be looking for that if I start going to the mountains. But, more climb rate can only help. :)
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Of course, but in the mean time it eliminates the need for "super twins". Just about anything that has turbochargers will work, but the key to OEI performance in any twin is weight. If you're flying out of ASE and not in a jet, even with an ADP, you're not going to be thrilled with what you're going to be seeing out the window if you lose an engine. You might not hit it, but you're going to get up close and personal with it. The key is weight management and that means minimum fuel. GJC would be a nice place to stop in your piston twin after an ASE departure.
 
Dead Stick said:
Of course, but in the mean time it eliminates the need for "super twins". Just about anything that has turbochargers will work, but the key to OEI performance in any twin is weight. If you're flying out of ASE and not in a jet, even with an ADP, you're not going to be thrilled with what you're going to be seeing out the window if you lose an engine. You might not hit it, but you're going to get up close and personal with it. The key is weight management and that means minimum fuel. GJC would be a nice place to stop in your piston twin after an ASE departure.
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I agree with your points. If we moved to a mountainous area we would probably either look to upgrade planes (based on our preferences and risk tolerances) or else have significantly different personal minimums. Here in the flatlands, our 310 has acceptable performance for our risk tolerance level.
 
What about the old super-charged Twin Bonanzas? They hauled a lot, if not very fast, and had better OEI climb than most.
 
My P baron is 650 payload with full fuel and 800 with mains only fuel. Mains would give about 4.5 hours of endurance. At gross, there wouldn't be great single engine performance, but it met cert criteria. Sounds like turbine country for your criteria.

Best,

Dave
 
Dave Siciliano said:
My P baron is 650 payload with full fuel and 800 with mains only fuel. Mains would give about 4.5 hours of endurance. At gross, there wouldn't be great single engine performance, but it met cert criteria. Sounds like turbine country for your criteria.

Best,

Dave
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I guess so, doesn't seem at first glance to be quite so challenging.

We should call it King Air Country.
 
The old Twin Beech 18 did a pretty good job, Methow Air flew them up to the time they went bankrupt trying to keep them flying.
 
An Aerostar can do it, especially the later 700, 702's and Superstars. They have 350hp aside.

The Merlyn converted Aero Commander 500B's can do it. Another 350hp per side airplane. And if you're not terrified of geared engines, then a 680F or a 560F could also do it with their supercharged Lycomings.
 
I wouldn't buy an IGSO Lycoming.

I hadn't thought about the Aerostars, those would make good options as well, although I'm not sure the useful load and gross weight on the 700s. Pressurization would be nice out there.
 
Alexb2000 said:
No fuel payload of 800 minimum, 1000 would be better. At least 700NM range with generous IFR reserves hauling those weights. I'm not a big stickler for speed with $6 gas, 180 would be fine in economy cruise.
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Cessna 401/402 should do what you want. Navajo Chieftan (aka PA31-350, mentioned above), too.
 
My King Air with -21s has 1,000 pound payload with fuel fuel. An STC is available that will increase that 700 pounds by adding 10 ply tires and some placards.

Best,

Dave
 
Inverted said:
PA31-350 would fit your needs perfectly.
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Ron Levy said:
Cessna 401/402 should do what you want. Navajo Chieftan (aka PA31-350, mentioned above), too.
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OEI performance on those won't be quite what Alex is looking for. Additionally, fuel burn on those is high enough and tankage low enough that he won't get the 700 nm range + IFR reserves he's looking for.
 
Ted DuPuis said:
OEI performance on those won't be quite what Alex is looking for. Additionally, fuel burn on those is high enough and tankage low enough that he won't get the 700 nm range + IFR reserves he's looking for.
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-350 can do 4 hours with reserve. It could easily get 700nm range if you play altitudes right. 4400 empty with a 7000 MTOW.
 
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