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checkride in two days


coanda
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hey all,

I have been cramming for my commercial lately and found out yesterday that my checkride is in two days. I'm not too worried I've been prepping for a while. Anyway as we all know each DPE has there own little trick questions and most of the time you are warned about them and have the time to figure them out before your ride. Here's one I can't (and none of the CFI's) get really solid answer on.

 

Why doesn't the 269c-1(CBi) have an out of ground effect hover chart?

 

Now we all know that the engine isn't derated, and you can pull in anything you can get, and the minute you lift off the ground (or even on the ground) due to the atmosphere your not at your full 180 hp. These answers have all been given to the DPE and all have been correct but he/she was always looking for something else.

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Have you checked out this great resource. Just looked at it the other day and i'm really impressed. You can download a free evaluation.

 

http://www.dauntless-soft.com/PRODUCTS/Rid.../helicopter.asp

 

it helps with the oral checkride questions. You never know, it may well answer your question. Good luck on the big day.

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hey all,

I have been cramming for my commercial lately and found out yesterday that my checkride is in two days. I'm not too worried I've been prepping for a while. Anyway as we all know each DPE has there own little trick questions and most of the time you are warned about them and have the time to figure them out before your ride. Here's one I can't (and none of the CFI's) get really solid answer on.

 

Why doesn't the 269c-1(CBi) have an out of ground effect hover chart?

 

Now we all know that the engine isn't derated, and you can pull in anything you can get, and the minute you lift off the ground (or even on the ground) due to the atmosphere your not at your full 180 hp. These answers have all been given to the DPE and all have been correct but he/she was always looking for something else.

 

I think your instructor owes you that one...

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Maybe they forgot to put it in there?

 

Maybe IGE and OGE hover performance is the same?

 

If you have that Schweizer book, look for something about performance and see if you can corelate any information that is true about both scenerios. If not, say it's a typo.:)

 

Later

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IGE and OGE performance is never the same. It always takes more power to hover OGE, in any model, under any conditions. The only reason I can think of for not having the OGE charts is if it can't hover OGE. However, I know that's not true. Well, I can think of another reason - the flight manual isn't complete.

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Its been a few months, but I think I remember seeing a OGE chart in the manual of a 300c, but I think it was in a different section then the IGE chart. One last thing, I was under the assumption the Cbi was a derated engine, at least derated from the 300c at 190hp. Not sure that this matters, but my .005 worth!

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Its been a few months, but I think I remember seeing a OGE chart in the manual of a 300c, but I think it was in a different section then the IGE chart. One last thing, I was under the assumption the Cbi was a derated engine, at least derated from the 300c at 190hp. Not sure that this matters, but my .005 worth!

 

 

Rog- not sure which engine you are speaking of. I know the HIO-360 G1A is rated at 180hp...not de rated to 180..( thats at 2700 rpm). The D1A version does 190hp at 3200 rpm.. I dont think either are really de rated in a 300 aircraft.

 

As for the original question, its probably a goofy answer, like Witch's they forgot to include it in the documentation...... ask him/her why the R22 can fly faster than the R44 with the doors off (according to the VNE limits in the POH).

 

 

You dont have to know it all to pass !! Good luck, Goldy

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WOAH!?! Hold on you guys and gals.

 

To answer the original question... there is no hover out of ground effect chart for the CBI, or the Hughes 269 A or B for that matter. The C does have a HOGE chart but that has no direct correlation to the other models. That chart is not required. It is not in the flight manual...

Oh gosh, gee, no chart, what do I do. Well if the DPE asks how you can find HOGE performance you can give one of the typical methods of determining that performance (there are a few threads you can search that have covered this topic and I would provide them but I haven't figured how to include them) That is the full throttle max manifold pressure type check just like hover ceiling check then add a couple inches more manifold needed for OGE to be safe. (I'm generalizing here)

 

The real key here is that if it isn't in the POH there isn't a prescribed performance for the aircraft so NO answer is the book answer, an estrapolation is the best that can be predicted for the aircraft.

 

The 300C is a derated engine . The 300CB/I is not derated, you can pull as much power as it can make. The fact that it isn't quite making full power due to density altitude or loss thru the induction system doesn't have any bearing on not having a HOGE chart. The chart was not required for certification, that is the short answer.

Edited by apiaguy
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I just looked in my manual and there 100% for sure is NOT an HOGE chart in it. Several IGE charts for the different engines though.

 

NO idea how I'd answer that question either, but at least now I'm thinking about it.

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No OGE chart, There are 2 IGE charts, one mixture full rich, one leaned.

As Apiaguy said, It wasn't required when the 300 was certified, so it isn't there, that is what I've been told anyway.(Is the OGE chart required now?)

 

There is reference to the OGE ceiling in the "General Specifications" section in the front.

 

Schweizer 300CB

*Hover Ceiling IGE 7800 FT

*Hover Ceiling OGE 5600 FT

 

*Based on 1550 pounds

 

Good luck with the ride

 

Fly Safe

Clark B)

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The 300C is a derated engine . The 300CB/I is not derated, you can pull as much power as it can make.

 

The 300C engine is NOT derated. It is rated for 190 horsepower at 3200 RPM, but it is capable of producing more power than it is rated to produce. Although the engine CAN produce up to 220 HP (or so I am told) the engine components are not designed to run at that high a power setting. A derated engine is capable of producing more power than it is rated for (in that aircraft), but it also will not damage itself by producing power in excess of its rating. Typically an engine is derated to increase TBO time, or because other components (transmission, drive shafts. etc.) cannot handle the engines full power. The other reason an engine is derated is to allow it to produce full power when flying above sea level. There is a difference, no matter how small it is.

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I disagree and you proved yourself wrong by your own admission.

 

 

"The other reason an engine is derated is to allow it to produce full power when flying above sea level. "

 

The HIO-360-D1A installed in the 300C may have "190 hp at 3200rpm" on the data tag indicating its rating but YOU as the pilot are responsible for not exceeding that power rating by not utilizing more than 26 inches manifold at sea level....

 

That engine IS DERATED to allow it to maintain 190 hp up to 4200 feet.

If you pulled more than 26 inches manifold you would exceed 190 hp. Just because the engine manufacturer does not rate the engine at its full potential doesn't mean it is not derated. The airframe manufacturer requested this engine specifically so that it can maintain rated power to a higher altitude without turbo/supercharging.

 

The engine IS capable of more power reliably.... look at the Enstrom making 225 hp with the turbo. (not to say the engines are the same... just the same basic design)

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THREAD HIJACK!!!

 

Out of curiousity, what would happen if you pulled all the power with a manifold pressure of say 29"? Would the engine blow up? Would the engine suffer severe damage from a high pressure for an amount of time like five minutes? What exactly makes an engine derated? How does one physically derate an engine? Why am I asking these questions?

 

Just wondering.

 

Later

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1. What would happen if you pull all available power for say 5 minutes?

The engine would probabally operate normally, but you have operated it beyond what the factory has established as a reliable margin

That is not to say you wouldn't possibly damage it... spin a bearing, break a connecting rod bolt, blow a jug, drop a valve... not likely on that engine if it is low time, but possible.

 

2. What exactly makes an engine derated? How does one physically derate an engine?

Derated egine: means an engine restricted to power less than potential maximum... We typically speak of engines that have a "thermodynamic potential" to develop a certain amount of power and then "derate" that engine for a particular application so that it is more reliable, not stressed to the max all the time.

As we ascend the air becomes less dense, normally aspirated recip engines and turbine engines alike lose power as you go up. By utilizing a derated engine you are able to keep full power (at least full power for the application or airframe) to a higher altitude because we were never asking the engine to give us full power at the lower altitude, we were merely restricting how much throttle we wanted you to give it.

So we physically derate it by putting a placard on the panel that says "do not exceed XXX manifold pressure"

 

 

The debate here between Photoflyer and myself is kind of rediculious and anyone could debate the technicalities of either side...

He is saying because lycoming "rates" the engine at 190 HP and that is what the maximum usable in the 300C is...... that it is not derated.

I'm saying that the potential of the engine is greater than 190 hp even though schweizer/hughes has limited it by manifold pressure. This makes it derated regardless what lycoming has put on the data plate as the "rated power"....

 

3. Why are you asking these questions?

I have no idea... you have way too much time on your hands like the rest of us.

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Let me put this into perspective. My motorcycle (SV650S) produces 64hp according to the engine manufacturer. Through modifications the same engine can be made to produce 90 or more HP (I've heard as high as 97hp). Does that mean the engine is derated? No, and the D1A is the same concept. Although the engine can be made to produce more than 190HP, it is not designed to. What happens to a SV engine when it produces more than 64hp? Broken crank, spun bearings, bent push rods, etc. Further, look in the general description of a 22 and it CLEARLY says it produces 160hp (not sure if thats correct) derated to 131hp. Show me where it says the 300C engine is derated. Although it is an argument of semantics, it could be an important distinction in the eyes of an examiner. Don't believe me? Just call Schweizer...we have...

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This is rediculious. Your motorcycle comparison is apples to oranges. If any examiner made a point out of this they are not testing you on anything but their personal agenda because it is not an important distinction in this situation. Just because the R22 is limited to 131 and the engine can produce 180 doesn't mean you can use 180 hp. It is the same thing as the 190 hp rating. The airframe and engine manufacturer designed the engine to be operated at less than full power so that it can maintain 190 hp to a higher altitude. Is that not derating? You are getting certification issues intermingled on this one.... of course schweizer is going to say it is only "rated" for 190hp. I actually can't believe you called them for that one. lol

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Apple and oranges are still fruit. The question of why the manufacturer derates an engine has no bearing on the operation of an engine, but it gets asked despite this. Translating tendency (theory) has no bearing on the physical act of hovering a helicopter, but it still gets asked. I am not saying that it has no bearing at all or that we shouldn't teach it, but if you didnt know what translating tendency was you could still keep the helicopter stationary. Then, by your logic, translating tendency is an examiners personal agenda. Just because a distinction is small, and as I admitted just a matter of semantics, it doesn't mean that it isn't important. And why wouldn't we call Schweizer? I'm no mind reader, and I'm not going to invent a reason why they rated a particular engine the way they did. If you are going to give a reason why it is (or isn't) derated wouldn't you want the REAL answer, and not something that your CFI invented because he didn't want to do the leg work.

 

For the sake of this thread, I suggest we take this to PMs.

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