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 Post subject: Navajo Props
PostPosted: Wed Jan 25, 2012 7:33 pm 
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Question for you experienced navajo drivers out there. Just started flying a Navajo with Hartzell props. To put it mild the performance is just not there compared to other navajo's I have flown. Talked with lots of other Ho drivers and there performance is much better compared to our navajo. The only big difference ( besides us having a bad paint job and a slightly higher OEW) is these other operators are running mccauley props. Want to know if the different props should make this much of a difference or if I am just driving a real shit bird.

Any experiences with this would be much appreciated.
Cheers



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 Post subject: Re: Navajo Props
PostPosted: Wed Jan 25, 2012 8:47 pm 
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Sounds like it is a certified shit bird! gne!


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 Post subject: Re: Navajo Props
PostPosted: Wed Jan 25, 2012 9:00 pm 
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Which ho? Was just involved with a 325 CR with 3 blade Hartzells that had nearly a 3000fpm climb. Partially stripped down for cargo transport though.


Last edited by DanWEC on Sat Mar 17, 2012 9:18 pm, edited 1 time in total.

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 Post subject: Re: Navajo Props
PostPosted: Wed Jan 25, 2012 10:48 pm 
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This was posted in another thread but has been a source of performance issues. Most people do not fully understand this system so be careful who explains it to you. Changing the density controller settings effect the max power available from the engines for take off and max power settings.


Quote:
With few exceptions.
Most importantly, and other 350 drivers can confirm, the ac will not be able to maintain altitude with one engine out, feathered or not. It will on paper, but not in practice. This is because operators will degrade (turn down) the maximum available boost level at max power. They do this for operational reasons to reduce wear and make use of full TBO numbers. If red line boost level is not available at max power, altitude can not be maintained at GW.
All manuals quote "red line power".
What is their "unwritten" standard maintanence procedure here? What are their setting?

Disclaimer: "The following statements are designed to be informational in nature, not speculative as it relates the accident that started this thread"
As an AME and a private (non multi rated) pilot. I have to say that the pa 31-350 is my favourite piston twin. It always amazes me that an aircraft that has been around so long still continues to have some of the same misconception follow it. In reference to the statement made above I can attest to the fact that some maintenace facilities turn down the density controllers on these engines to "save" the engine and or recomend part power take offs. I have always refused to do so or recommend part power take offs and here is why. The TIO 540 J2BD engine is a fine engine. The density controller is designed to "if set correctly" provide 350 HP when the throttle is on the stops props at 2575. on a standard day the manifold MP should read 42". On a non standard day the MP may read higher or lower to achieve 350 hp. Without the charts selecting your own MP for take may mean 300 hp one day 235 the next who knows. Max is 49. How much runway do you need who knows. The worse scenario is when maintenance turns down the dentity controller. Now the power available at the throttle stop will always be less than 350. The types of fields that navajos are capable of operating from can demand all 350 hp from both engines. Worse still in an engine out situation the remaining engine will need to be able to develop all the power it is supposed to. Piper Lycoming and Transport Canada have recommend against these practices but I still see the question here in the forums about part power take offs. If your company recommends part power take offs think again If maintenance has turned down the controllers get them set properly. As an AME I have always tried to give pilots all the tools they need to do the job. It is the pilots job to mange the engines, it is the AMEs job to make sure they get 350 hp to manage.

Fly safe



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 Post subject: Re: Navajo Props
PostPosted: Wed Jan 25, 2012 11:07 pm 
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Thanks for the responses.
For the record its a 350. The main performance issue i am seeing is with climb performance and cruise speed. Other navajo's i have flown climb at an easy 1000 foot per minute with a load on and cruise around 170 kts. This old "Ho" struggles to climb at 500 fpm a couple hundred lbs below max gross and likes to cruise around 145 to 150. I use about 31" and 2250 rpm @ 5000'. According to the performance charts I should be getting 230 hp a side and 170 Ktas. Also thought it may just be an indication error but the airspeed on the dial and g/s on the GPS seem to match within a few knots on the roll.



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 Post subject: Re: Navajo Props
PostPosted: Thu Jan 26, 2012 2:37 am 
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most likely the case is what hoptwoit said.


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 Post subject: Re: Navajo Props
PostPosted: Thu Jan 26, 2012 2:16 pm 
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Probably way out of rig flight controls, and a gear door or three hanging open in the wind.
It's not uncommon to gain more than 10 kts after rigging properly.



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 Post subject: Re: Navajo Props
PostPosted: Fri Mar 16, 2012 8:48 pm 
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If you were to read the Piper AFM and/or the Lycoming pilots handbook, there is a statement in there to NEVER do a partial power take-off, EVER. The last bit of throttle movement introduces extra fuel that will provide internal cylinder cooling and prevent detonation. IMHO, if owners and/or operators are dialing down the density controller to "save" the engine to reduce costs, tell them to go buy an Aztec or some other cheap airplane rather than risk the lives of pilots and passengers. From your description, it appears you either have engine problems, indication problems or a wing/flaps/flight control missrigging. Lots of luck, you may need it.


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 Post subject: Re: Navajo Props
PostPosted: Sat Mar 17, 2012 12:46 am 
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hoptwoit wrote:
This was posted in another thread but has been a source of performance issues. Most people do not fully understand this system so be careful who explains it to you. Changing the density controller settings effect the max power available from the engines for take off and max power settings.


Quote:
With few exceptions.
Most importantly, and other 350 drivers can confirm, the ac will not be able to maintain altitude with one engine out, feathered or not. It will on paper, but not in practice. This is because operators will degrade (turn down) the maximum available boost level at max power. They do this for operational reasons to reduce wear and make use of full TBO numbers. If red line boost level is not available at max power, altitude can not be maintained at GW.
All manuals quote "red line power".
What is their "unwritten" standard maintanence procedure here? What are their setting?

Disclaimer: "The following statements are designed to be informational in nature, not speculative as it relates the accident that started this thread"
As an AME and a private (non multi rated) pilot. I have to say that the pa 31-350 is my favourite piston twin. It always amazes me that an aircraft that has been around so long still continues to have some of the same misconception follow it. In reference to the statement made above I can attest to the fact that some maintenace facilities turn down the density controllers on these engines to "save" the engine and or recomend part power take offs. I have always refused to do so or recommend part power take offs and here is why. The TIO 540 J2BD engine is a fine engine. The density controller is designed to "if set correctly" provide 350 HP when the throttle is on the stops props at 2575. on a standard day the manifold MP should read 42". On a non standard day the MP may read higher or lower to achieve 350 hp. Without the charts selecting your own MP for take may mean 300 hp one day 235 the next who knows. Max is 49. How much runway do you need who knows. The worse scenario is when maintenance turns down the dentity controller. Now the power available at the throttle stop will always be less than 350. The types of fields that navajos are capable of operating from can demand all 350 hp from both engines. Worse still in an engine out situation the remaining engine will need to be able to develop all the power it is supposed to. Piper Lycoming and Transport Canada have recommend against these practices but I still see the question here in the forums about part power take offs. If your company recommends part power take offs think again If maintenance has turned down the controllers get them set properly. As an AME I have always tried to give pilots all the tools they need to do the job. It is the pilots job to mange the engines, it is the AMEs job to make sure they get 350 hp to manage.

Fly safe



Thank You for that information. I had the pleasure of flying the highest time Navajo in the world once. Piper wanted to buy it back and tear it apart. I haven't flown one in many years but ... I have flown them with hockey teams and hockey equipment on board and on one stove it would have been a very busy day.

Thank information was great to have in the memory bank.



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 Post subject: Re: Navajo Props
PostPosted: Sat Mar 17, 2012 12:57 am 
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Joined: Wed Dec 01, 2010 5:28 pm
Posts: 203
oldtimer wrote:
If you were to read the Piper AFM and/or the Lycoming pilots handbook, there is a statement in there to NEVER do a partial power take-off, EVER. The last bit of throttle movement introduces extra fuel that will provide internal cylinder cooling and prevent detonation. IMHO, if owners and/or operators are dialing down the density controller to "save" the engine to reduce costs, tell them to go buy an Aztec or some other cheap airplane rather than risk the lives of pilots and passengers. From your description, it appears you either have engine problems, indication problems or a wing/flaps/flight control missrigging. Lots of luck, you may need it.


FYI ... I flew a Cessna 401 for a while. We sent that airplane away and it came back with NEW ENGINES on it and it never ever ran right from the day it showed up. I started to take trends on a sheet of paper for every altitude in cruise at least once or twice a day. When maintenance saw that I wasn't making this stuff up .... the aircraft finally went back to the place they (the engines ) were installed. ( Ithink it was Clevland Ohio ) I think the end casue was when the engines were put together the WRONG FUEL SERVO's were installed. .... I am not telling you this is the cause. BUT

START WRITING DOWN TRENDS FOR CRUISE AND INCLUDE ALTIMETER AND OAT. write down each engine vertically the the same info the same way every day and in a few days you will see a pretty good picture. Include fuel flows, indicated airspeed, MP, RPM, everything.Then I would sit dawn with your favorite machanic and have a sharing of ideas.

Good luck and fly safe.



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