Power Checks

[displayname]

QUESTION: When you have a plus 5 engine (allison) are we only pulling 95% tq when indicating 100%

therefore could we pull 105% without over torqueing. thats one question.

 

QUESTION: Will a plus 5 engine outlift a negative engine at sealevel

 

understanding that the plus engine is working easier. just a discussoin having here

[Reddog]

If you have a "+" engine it means that your N1 and/or engine temp will be lower than a "0" or minus for the same torque value at the same environmental conditions.

[Over-Talk]

A power check is a measurement of how hard (hot) your engine must work to produce 100% torque compared to a 'standard' engine..........not how much you can lift!!

If your engine meets or exceeds the 'standard', then you will be able to achieve the weights shown in the "performance" charts of the flight manual. That is how much you can lift!!

 

Here's why........

A turbine engine has two ends........one end has a bunch of fuel and air mixing together, the other end has a driveshaft coming out of it that twists to turn something.

 

Some engine manufacturers have a 'standard' figure of how much fuel and air (i.e heat) should be needed to produce a certain amount of twist (torque) in that shaft.

Other manufacturers prefer to tell you how much twist/torque should be produced from that measued temperature level.

 

If an engine is running well it will take less fuel and air to produce the same amount of torque than an engine that is running badly.

For example, this is described by saying it is running 30 degrees cool, or it is a plus 5% engine (depending on the type of scale the manufacturer prefers).

 

The answer to question 1; the plus 5 engine is producing 100%, but the manufacturer's chart says a 'standard' engine would only produce 95% for the engine temperature (TOT,EGT,ITT,T4,T5) that was measured.

Therefore you are getting alot of "bang" for your "buck". This is a 'cool' or 'good' engine.

Do NOT pull over the torque limit, just be grateful you have a strong engine that isn't working too hard to produce that much power.

 

Answer 2: Just because it is a 'negative' engine, it doesn't mean it won't reach 100% torque. It just means it will be 'hotter' than a 'standard' engine.

A plus 5 engine might out-lift a negative engine......it depends on the engine temperature needed to produce 100% torque, or whether both engines get to the 100% torque limit first.

That is, if the engine is really bad, its temperature will be so high that you will reach the TOT,EGT,ITT,T4,or T5 limit before reaching the 100% torque limit, and will have to stop pulling at less than 100% torque.

Therefore you will lift less.

[snark]

uhhhhh.......Whoever you work for may need to start doing daily overtorque inspections. Just a note of caution......if you see paint flaking off the mast........stop, look, and listen. An engineer will be hunting you down.

[displayname]

first of all, this was only a discussion in house. the above write-up by over-talk was exactly how we thought. so no over torque is ever exceeded. its just a performance thing for the engine.

and i work for a good company that we all have open discussion on anythin. sometime over a bevy.

 

 

uhhhhh.......Whoever you work for may need to start doing daily overtorque inspections. Just a note of caution......if you see paint flaking off the mast........stop, look, and listen. An engineer will be hunting you down.

[sharkbait]

The way it was explained to me :

A power check chart is a "paper" engine and tells you that , for example, at 26 Deg C at 1000 ft PA the engine should need "X" N1 or NG or whatever and "Y" T4 or ITT or whatever term they use to produce a given torque.

If your engine produces the same torque with a lower N1 and T4 then your engine is better than standard. If your engine needs a higher N1 and T4 to produce a given torgue then your engine is worse than standard.

Some power checks want you to pull a given torque and cross reference N1 and T4, some want you to pull a given N1 and cross check torque.

All the same in the end you just want to make sure that your engine is equal to or better than the "paper" engine.

By keeping a record of power checks we can see if the engine is remaining the same or deteriorating - sometimes they will actually improve after a compressor wash.

A sudden radical change needs to be investigated - sometimes there is actually a problem with the engine or it may be a guage problem.

Some factors that lead to weird readings are cross wind or downwind vs into wind and bad OAT readings - always try to cross ref the OAT with another source. Nothing like changing the engine only to discover that the OAT guage is reading 5 deg low or better yet you have used the wrong chart for the installation ( particle seperator, snow baffles ect)

[skywrench1]

If your engine meets or exceeds the 'standard', then you will be able to achieve the weights shown in the "performance" charts of the flight manual. That is how much you can lift!!

 

Well said O.T. While it is "nice" to have a +12 "stump puller", in doing so flight manual performance may well be exceeded even if 100% torque (or Ng as the case may be) was the maximum parameter reached during that excercise. A spec. engine will deliver flight manual performance (which is what we are being paid for) as doggish as it may seem.

 

A sudden radical change needs to be investigated - sometimes there is actually a problem with the engine or it may be a guage problem.

Some factors that lead to weird readings are cross wind or downwind vs into wind and bad OAT readings - always try to cross ref the OAT with another source. Nothing like changing the engine only to discover that the OAT guage is reading 5 deg low or better yet you have used the wrong chart for the installation ( particle seperator, snow baffles ect)

 

As Sharkbait has stated, ensure the OAT is accurate and equally important verify your torque and temperature calibrations and if you N1 figures into the equation better ensure that indicator is not the culprit. Also, there better not be any air and heater system leaks, they'll contribute to poor engine performance.