Derated 145 HP

[boardutah]

My question is for any Robinson R22 pilots. Total BHP (brake horse power) is 180. Robinson tells us that that 180 total is derated to 145 BHP. why 145?? what is the 145 used for? I understand why engines are derated - but what exactly is the 145? max continuous is 124 which means whenever you are using your max continuous power setting (MAP) you are using 124 BHP from the engine - and the same applies with the 5 min take off of 131 BHP. what is the purpose of that 145?

[Wannabe1]

Altitude

[Pogue]

The O-360-J2A is not rated at 180 like most of the O-360s, the engine manual rates it at 145. My understanding is that is due to some of the weight reduction done for the R-22 by Lycoming. So they derated the engine to keep from exceeding temperature limits. Robinson further derates it to 124/131 which from what they said in the factory course was as much for reliability as for better performance at altitude. I don't have the book handy but I believe the O-320 in the R-22 Beta has a higher output per Lycoming even though it's also rated at 124/131 in the R-22.

[RockyMountainPilot]

Yes, the O-360-J2A has a limitation of 145HP due to some lightening of the engine. However, it is still capable of producing 180HP and if you pull the collective into your armpit at sea level, you will get close to 180HP. The 145HP limitation is suppose to be maintained by the pilot. Of course, the Robinson has the 124/131HP limitation as well.

 

The reason it can produce 180HP is that as you climb in altitude, you lose power starting at 180HP, and not the 160HP of the O-320's.

[Marc D]

And just for a little clarification. Lycoming said to Robinson "We will not certify this engine for 180hp; how much do you need?" Robinson: "We will only be using 131hp, so how about 145hp." Lycoming: "We can do that." This is how the random number of 145 came about.

Straight from Mr. Robinson's mouth about 12 years ago.

 

Marc D.

[Tenacious T]

The drive train is also not designed to withstand sustained 180hp input

[Goldy]

The drive train is also not designed to withstand sustained 180hp input

 

 

Correct- Especially the T/R gearbox and driveshaft...and as far as lightening the engine, part of that reduced the thickness of the cylinder walls, which is why Lycoming pitched for a decreased HP number.

[DieselBoy]

They also wanted to have a little reserve power since people over pull all the time.

[boardutah]

thanks for the answers so far. also thanks for filling me in on how they came up with 145 BHP, i wasn't aware of that. however my question really hasn't fully been answered yet. I am fully aware why engines are derated and that the o360 has a total of 180 HP that is actually AVAILABLE - but what is the PURPOSE of 145HP? when would you use over 131HP (5 minute take off) let alone 145HP?? and how do you know when your using 145 HP?

[DieselBoy]

When you figure out your MCP (124hp) using the placard, you then add 0.9" MAP for the takoff power (131). That's a 7hp difference. The primary use for a 22 is flight training and students WILL over pull the power. If I understand correctly the 145 allows room for this, almost 2" of MAP over takoff power.

 

Derating the engine for it's many purposes also resulted in a higher TBO, which Frank wanted.

Edited December 4, 2008 by DieselBoy

[Wannabe1]

RockyMountainPilot answered your question. Have you ever driven in the mountains? Those turbocharged trucks seem to keep their power, your car with it's carburetor seems to be missing power? On your R22, you control the MAP and will have more available (still keeping it under 124) at altitude. The 145 is an arbitrary number. Could as well have been 150 or 174.3. Maybe the engine mfger and Robinson couldn't agree on 180 so they picked 145, really doesn't matter.

 

 

 

thanks for the answers so far. also thanks for filling me in on how they came up with 145 BHP, i wasn't aware of that. however my question really hasn't fully been answered yet. I am fully aware why engines are derated and that the o360 has a total of 180 HP that is actually AVAILABLE - but what is the PURPOSE of 145HP? when would you use over 131HP (5 minute take off) let alone 145HP?? and how do you know when your using 145 HP?

Edited December 4, 2008 by Wannabe1

[jehh]

Actually, not all O-360s make 180hp. Some make 160hp, some make over 210hp, it depends on the engine design and RPM used. The 360 is just the displacement of the engine, a lot more goes into an engine's power output than that.

[justfly]

Recently apiaguy did a very nice job of shedding some light on this topic in a post:

O-320-B2C vs. O-360-J2A SPECS

[R22 Driver]

I believe that another reason for the derating is to allow MTBO of 2,200 hours, to coincide with the airframe overhaul.

 

A non derated O360 or O540 have MTBO of 2,000 hours.

[RockyMountainPilot]

Actually, not all O-360s make 180hp. Some make 160hp, some make over 210hp, it depends on the engine design and RPM used. The 360 is just the displacement of the engine, a lot more goes into an engine's power output than that.

 

 

Most all lycoming O-360's are capable of making 180HP or 168HP. I do not know of one that makes over 180HP. You might be thinking of an IO-360. 8.5 Compression gives you 180HP, and 7.2 gives you 168HP. The O-360E has a 9:1 compression which suggest it can produce over 180HP, but it may have a MAP limitation to keep it below 180HP. Anyone flown anything with a -E? RPM and compression ratio are the same in the O360J and other 180HP rated models. So it can produce 180HP, however, it is only placarded for 145HP. Many engines can produce much more horsepower then which they are rated. They often require the pilot to limit the power output manually. In the Cirrus I fly, I often see the power scale show 105% or 110% on a cold day. I simply pull the RPM back until it shows 100%.

[Marc D]

thanks for the answers so far. also thanks for filling me in on how they came up with 145 BHP, i wasn't aware of that. however my question really hasn't fully been answered yet. I am fully aware why engines are derated and that the o360 has a total of 180 HP that is actually AVAILABLE - but what is the PURPOSE of 145HP? when would you use over 131HP (5 minute take off) let alone 145HP?? and how do you know when your using 145 HP?

 

I thought I answered it. 145hp is a total random number(almost). Lycoming was not willing to allow the chance of this engine being used in something else and run at 180hp. It would not stand up to the TBO. It will produce 180hp at sea level, but must not be allowed to. Lycoming must put a tag on the engine when they manufacture it. They would NOT put 180hp on it. They asked Mr. Robinson how much he needed. He said that he only needed 124 for continuous use and 131hp for occasional use. They RANDOMLY chose a number that satisfied Mr. Robinson's need and was low enough to satisfy Lycoming's need. Lycoming is basically saying that if someone pulls this engine out of the Robinson and wants to use it in something else, it is not allowed to be operated over 145hp. It has absolutely nothing to do with operations in the R22. You are never legally permitted during normal operations to use over 131hp.

 

Marc D.

[jehh]

Most all lycoming O-360's are capable of making 180HP or 168HP. I do not know of one that makes over 180HP. You might be thinking of an IO-360.

 

Yep, I was...

 

So it can produce 180HP, however, it is only placarded for 145HP.

 

I'm not so sure... While you might be right, then explain the difference between the A and C engines? Other than very minor size differences, there should be no point to both.

 

It would be interesting to hook a J2A engine up to a dyno and see what it really outputs... *shrug*

[jehh]

I thought I answered it. 145hp is a total random number(almost). Lycoming was not willing to allow the chance of this engine being used in something else and run at 180hp. It would not stand up to the TBO. It will produce 180hp at sea level, but must not be allowed to. Lycoming must put a tag on the engine when they manufacture it. They would NOT put 180hp on it. They asked Mr. Robinson how much he needed. He said that he only needed 124 for continuous use and 131hp for occasional use. They RANDOMLY chose a number that satisfied Mr. Robinson's need and was low enough to satisfy Lycoming's need. Lycoming is basically saying that if someone pulls this engine out of the Robinson and wants to use it in something else, it is not allowed to be operated over 145hp. It has absolutely nothing to do with operations in the R22. You are never legally permitted during normal operations to use over 131hp.

 

Marc D.

 

Interesting... I haven't heard this story before, but of course that doesn't mean it isn't true.

[Marc D]

Interesting... I haven't heard this story before, but of course that doesn't mean it isn't true.

 

 

Like I said in an earlier post, this is from a discussion I had with Mr. Robinson 8 or 10 or 12 years ago. I had the same question, so when I was at the factory, I asked him.

 

Marc D.

[RockyMountainPilot]

Yep, I was...

 

 

 

I'm not so sure... While you might be right, then explain the difference between the A and C engines? Other than very minor size differences, there should be no point to both.

 

It would be interesting to hook a J2A engine up to a dyno and see what it really outputs... *shrug*

 

 

The main difference between the O-360 A & C models is the mounting. C is for conical mounts, and A is for dynafocal mounts.

 

If you look on the TCDS, you will see the MAP limitations on the O-360 J2A. If you open the throttle more, you will exceed the 145 HP limitation.