Tiger Performance?

[poadeleted3]

I'll write about our trip to WV in a little while, but I wanted to ask about the performance I got from our Tiger this weekend. The plane was one of Tiger Aircraft's new planes.

The instructor when I checked out said to maintain about 2400 rpm for cruise, and Anthony Amorosi has mentioned the same rpm, I think. Now, in the Skyhawk SP with almost the same engine, 75% requires 2550 to 2600 rpm. On our trip this weekend, I held 2400 rpm, and looking at the book performance and the fuel I burned I don't think I was pulling even 65% power. We were at 6500 feet on the way there, and 7500 feet on the way back. We only got 118 knots TAS both ways. Now frankly, that's not the speed I've been led to expect out of the Tiger, and isn't any better than the Skyhawk SPs. I also only burned 22 gallons getting there, for a fuel burn of 7.3 gph. I leaned until rough, then enriched a bit, and kept the mixture rich enough to keep the CHT under 400. Obviously, I wasn't pulling much power. What rpm do other Tiger drivers use?

 

[Ken Ibold]

The instructor when I checked out said to maintain about 2400 rpm for cruise, and Anthony Amorosi has mentioned the same rpm, I think. Now, in the Skyhawk SP with almost the same engine, 75% requires 2550 to 2600 rpm.

I don't have a Tiger book, but there is a point to be made here regarding "what instructors say." It's not uncommon for instructors to be really good at teaching something like primary flight training or whatever and to be absolutely inexperienced about using airplanes in the real world. I once had an excellent instructor who insisted that I select 2450 rpm cruise in a fixed pitch airplane under all circumstances. When I pointed out the effect of altitude on power production, the response was "oh, yeah, well, you're right. I never fly higher than 2,000 feet so that's what I use."

But I would like to issue the gentle reminder that your flight planning should have included looking up that number in the approved book before you left. And what about checking expected performance vs actual performance while enroute?

 

[Anthony]

I'll write about our trip to WV in a little while, but I wanted to ask about the performance I got from our Tiger this weekend. The plane was one of Tiger Aircraft's new planes.

The instructor when I checked out said to maintain about 2400 rpm for cruise, and Anthony Amorosi has mentioned the same rpm, I think. Now, in the Skyhawk SP with almost the same engine, 75% requires 2550 to 2600 rpm. On our trip this weekend, I held 2400 rpm, and looking at the book performance and the fuel I burned I don't think I was pulling even 65% power. We were at 6500 feet on the way there, and 7500 feet on the way back. We only got 118 knots TAS both ways. Now frankly, that's not the speed I've been led to expect out of the Tiger, and isn't any better than the Skyhawk SPs. I also only burned 22 gallons getting there, for a fuel burn of 7.3 gph. I leaned until rough, then enriched a bit, and kept the mixture rich enough to keep the CHT under 400. Obviously, I wasn't pulling much power. What rpm do other Tiger drivers use?

Absoltuely not. In my post on V-Speeds I said to use the appropriate RPM from the POH for the altitude and % horsepower you wanted. Hortman told the same thing to Adam Z. and its because they want a low fuel burn since its a wet rental. Looking at my POH, 2400 RPM at 6,500 ft. is 57% power at Standard Temp, 38F. At that setting you'll only get a True Airspeed (TAS) of 119 knots. At 65% power you'd get 130 KTAS and at 75% power, about 137 KTAS.

Joe, you were short changing yourself on speed. Your fuel burn of 7.3 GPH should have tipped you off that you were running very low HP. I usually run at 65% or 2,550 RPM's at that altitude getting 130 - 132 KTAS and averaging 9.5 GPH. Go back and fly it again!

 

[poadeleted3]

But I would like to issue the gentle reminder that your flight planning should have included looking up that number in the approved book before you left. And what about checking expected performance vs actual performance while enroute?

I bought the book for that very reason, and lo and behold, it says "75% power will give me such and such a speed." But, nowhere that I've found in the book does it tell me what 75% power is, darn it! I didn't find a placard either, though that doesn't mean I didn't miss it.

I also checked the actual POH in the plane, with the same results.

 

[poadeleted3]

Absoltuely not. In my post on V-Speeds I said to use the appropriate RPM from the POH for the altitude and % horsepower you wanted. Hortman told the same thing to Adam Z. and its because they want a low fuel burn since its a wet rental. Looking at my POH, 2400 RPM at 6,500 ft. is 57% power at Standard Temp, 38F. At that setting you'll only get a True Airspeed (TAS) of 119 knots. At 65% power you'd get 130 KTAS and at 75% power, about 137 KTAS.

Joe, you were short changing yourself on speed. I usually run at 65% or 2,550 RPM's at that altitude getting 130 - 132 KTAS. Go back and fly it again!

Yeah, 7.3 gph made it obvious that I wasn't pulling any power.

Where in the book did you find what RPM gives you what power? I haven't found that

 

[Anthony]

Yeah, 7.3 gph made it obvious that I wasn't pulling any power.

Where in the book did you find what RPM gives you what power? I haven't found that

My 1978 Grumman Tiger POH is probably different from the new Tiger Aircraft POH, but in mine its under Section 5, "Performance", Cruise Performance. There are tables for different RPM's showing HP, TAS, and Fuel burn for each altitude and three different temperature settings, 2F, 38F, 74F.

 

[Ken Ibold]

Hortman told the same thing to Adam Z. and its because they want a low fuel burn since its a wet rental.

And since they know it's a trip, that means more time on the Hobbs, too!! The owner gets the benefit times 2!

 

[Len Lanetti]

And since they know it's a trip, that means more time on the Hobbs, too!! The owner gets the benefit times 2!

Tripple actually if you consider reduced tach time/engine wear. The Hortman family has been renting aircraft since before Herb was born.

Joe, what altitude did you cruise?

Len

 

[gibbons]

Now frankly, that's not the speed I've been led to expect out of the Tiger, and isn't any better than the Skyhawk SPs.

Joe,

My logbook program has a feature that shows aircraft by type by speed, based on logged time and distance for cross country flights. It also calculates an adjusted speed by subtracting .15 hours for startup, taxi, etc. Not exactly scientific, but it yields pretty good results if enough flights are involved.

For the Gruman Tiger: 87 flights averaging 160 NM. Adjusted speed - 115 kts
For the C172 (not an SP): 20 flights averaging 120 NM. Adjusted speed - 93 kts

I think these are pretty accurate numbers for these two airplanes in real world situations. I'd be surprised if the C172 can keep up with the Tiger.

Chip

 

[poadeleted3]

Tripple actually if you consider reduced tach time/engine wear. The Hortman family has been renting aircraft since before Herb was born.

Joe, what altitude did you cruise?

Len

6500 there, 7500 on the way back.

 

[Anthony]

6500 there, 7500 on the way back.

That's right, I was giving you numbers for 6,500 ft. At 7,500 ft, the picture gets worse. You were only running 55% power for a 118 KTAS. I'll say one thing Joe, you got book performance out of that Tiger for the low RPM you were running. You must have leaned well. Good job. Herb will be thankfull.

7,500 - 8,000 feet is optimum altitude. You can run full throttle and still only be at 75% power, getting close to 140 knots on 10.8 GPH.

 

[AdamZ]

Joe:

There is a simple reason why you can't find the various Tach settings for % BHP in your Tiger POH. Its not there. No doubt you purchased for, let me guess $30.00, the POH for N1196G. You were sold a photo copy of the POH with a plastic Binder. If you look on the first page inside it is dated December 18, 1991. ( The Tiger you flew is not actually new but was refurbed as I stated in an AOPA post.) You really can't tell the difference though.
If you look in section 5 page 5-17 you will see the BHP% as it corresponds to fuel consumption and TAS at various altitudes and temps. Nowhere does it relate to a Tach setting . For example it just says at 6000' 65% BHP @ ISA+20 gives you 9.8 GPH and 125 TAS kts. Quite frankly without the help of folks like Anthony or Ron I don't know how else to figure it out other than by trial and error.
Anthony is dead on target. I have come to the conclusion that flight schools teach us The rules of the game, the "System" Safety, how to land take off get from A-B and not Kill ourselves. However they don't teach us how to "understand" the plane. Anthony is right I was taught to fly at 2400RPM like that was gospel. I believed that Full throttle was for Take off and climb only (2500rpm on climb). I thought that if I went over 2400 RPM in cruise the engine would blow up or melt or something to that effect. I had to actually ask to be taught to lean the mixture. I got through my PP and IR without ever being taught performance at various altitudes.( Now there is an argument for owning vs. renting). I still routinely find myself slipping back to setting the RPM@ 2400 even if I'm flying @ 6000' Just this past weekend as a matter of fact. I put 2.6 on the hobbs and burnt only 19.8 gallons that's 7.6gph. WHAT WAS I THINKING. Duh! I slipped back into that 2400 rpm myth.

Adam Zucker

 

[poadeleted3]

Joe:

There is a simple reason why you can't find the various Tach settings for % BHP in your Tiger POH. Its not there. No doubt you purchased for, let me guess $30.00, the POH for N1196G. You were sold a photo copy of the POH with a plastic Binder. If you look on the first page inside it is dated December 18, 1991. ( The Tiger you flew is not actually new but was refurbed as I stated in an AOPA post.) You really can't tell the difference though.
If you look in section 5 page 5-17 you will see the BHP% as it corresponds to fuel consumption and TAS at various altitudes and temps. Nowhere does it relate to a Tach setting . For example it just says at 6000' 65% BHP @ ISA+20 gives you 9.8 GPH and 125 TAS kts. Quite frankly without the help of folks like Anthony or Ron I don't know how else to figure it out other than by trial and error.
snip

Thank goodness!! I've been sitting here going through the book again, and still haven't found a table, graph or anything else telling me what rpm = what horsepower at various altitudes and temps. I was beginning to think I was blind! The Cessna Skyhawk SP performance section is marvelous in that regard.

I do have a copy of the book for 1196G, but that's not what I ended up flying. I got to fly N950TE, the beauty with the stars and stripes paint job. Talk about arriving in style

 

[AdamZ]

50TE is a nice plane. I flew in it with Ron, the Anameter was acting up then hope its ok now. I flew 957TE Sunday. Looking forward to seeing pictures.

Adam Zucker

 

[BillG]

Adam - that's exactly right. Good summary...! I had no idea how to lean or use anything other than 2400 RPM. When I finally get my Tiger (new plane swallowed a valve on my trip home - I think a lot of people know the story already though) I really need to figure out how to fly it properly!

Bill

 

[Anthony]

Its amazing the newer POH doesn't have the performance charts with RPM's. I'm sure they are on-line somewhere. If not, I can alway use the archaic method and fax them to you. Just let me know.

 

[Len Lanetti]

Lycoming Engine Performance?

Quite frankly without the help of folks like Anthony or Ron I don't know how else to figure it out other than by trial and error.

Lycoming sells an engine operators manual. I have one for the O360 series. It covers all variants of the engine (IO, TSIO, helicopter, aerobatic...). Tons of performance charts. Only down side is that someone over 40 will probably need a magnafying glass to read the charts in detail.

If a person got this book for the O360 and the one for the O320 they would probably be covered for a good 65% of the rental fleet.

Len

 

[Ken Ibold]

Re: Lycoming Engine Performance?

Lycoming sells an engine operators manual. I have one for the O360 series. It covers all variants of the engine (IO, TSIO, helicopter, aerobatic...). Tons of performance charts. Only down side is that someone over 40 will probably need a magnafying glass to read the charts in detail.

If a person got this book for the O360 and the one for the O320 they would probably be covered for a good 65% of the rental fleet.

Yes, but the issue with the books is they reference power settings to manifold pressure and rpm, which makes them less than ideal for a fixed-pitch airplane.

The current American Champion books have no power setting information, either. So we tend to use the charts from the Warrior II, which has a nearly identical engine variant and the same power spect -- and Piper's charts are excellent.

 

[Len Lanetti]

Re: Lycoming Engine Performance?

Yes, but the issue with the books is they reference power settings to manifold pressure and rpm, which makes them less than ideal for a fixed-pitch airplane.

Whoops, forgot about that little detail. Thanks Ken.

Len