Go Back  PPRuNe Forums > Aircrew Forums > Rotorheads
Reload this Page >

Power check technique for twin turbines

Rotorheads A haven for helicopter professionals to discuss the things that affect them

Power check technique for twin turbines

Old 26th Aug 2019, 01:06
  #1 (permalink)  
Thread Starter
 
Join Date: Apr 2016
Location: Surrey
Posts: 5
Power check technique for twin turbines

Could anyone enlighten me with an “on the job” technique method for power checking before going into a landing site. I currently fly light SEP’s and curious as to how you go about it on a big bird.
For info, one method I have been taught:
25kts gnd speed
check power
add 15% for IGE
add another 15% for OGE

thanks!
HeliHJ is offline  
Old 26th Aug 2019, 05:04
  #2 (permalink)  
 
Join Date: May 2008
Location: East of Africa
Age: 44
Posts: 894
I use this method:

Slow airspeed just above TL (usually around 40 knots, just before she starts to "shudder").
VSI zero
Ball centered
Crossing the area on a pre-determined heading

Then check:
Airspeed vs GS
Pitch setting vs power indicated
Track vs Heading

On the speeds, I can see exactly if I have estimated the winds at the area correctly.

Pitch setting vs power when VSI is zero shows me the same, plus I can read what my estimated power on landing will be (usually Power indicated pus 8-10 percent).

Track vs heading is all about the drift in case of wind again...

At unknown landing sites, I usually do a high recce, then a low recce including the power check, where I also check landing site elevation, last check for obstacles and approach path..


hueyracer is online now  
Old 26th Aug 2019, 11:28
  #3 (permalink)  
 
Join Date: Feb 2006
Location: Germany
Posts: 846
Just press the VMS Button (vehicle management system)
and look at the numbers on the bottom left ��
At least, if you fly a modern helicopter ��

​​​​​​​
Flying Bull is offline  
Old 26th Aug 2019, 12:39
  #4 (permalink)  
 
Join Date: Feb 2006
Location: On the big blue planet
Posts: 941
Originally Posted by Flying Bull View Post
Just press the VMS Button (vehicle management system)
and look at the numbers on the bottom left ��
At least, if you fly a modern helicopter ��​​​​​
Two different things. One is for engine health the other a rule of thumb for calculating powerrequirement for a given situation.

skadi
skadi is offline  
Old 26th Aug 2019, 13:55
  #5 (permalink)  
 
Join Date: Feb 2006
Location: Germany
Posts: 846
Originally Posted by skadi View Post
Two different things. One is for engine health the other a rule of thumb for calculating powerrequirement for a given situation.

skadi
for engine health you press the EPC (engine power check) button

the display on the bottom left in this sophisticated helicopter displays current weight (if you have entered pilot and crew / baggage weight correctly)
and what the helicopter is capable of doing with it at current ambient conditions
that is HIGE/HOGE AEO
CAT A VTOL possibility
30 sec / 2 min OEI HOGE
which gives a very clear picture of what to expect in case of 😏
Flying Bull is offline  
Old 26th Aug 2019, 15:16
  #6 (permalink)  
 
Join Date: Feb 2006
Location: On the big blue planet
Posts: 941

Thanks, pic was nearly unreadable on mobile phone..

skadi
skadi is offline  
Old 26th Aug 2019, 16:26
  #7 (permalink)  
 
Join Date: Feb 2006
Location: Germany
Posts: 846
Originally Posted by skadi View Post

Thanks, pic was nearly unreadable on mobile phone..

skadi
Well, the first photo was a screenshot out of a video - this one should be better


Flying Bull is offline  
Old 26th Aug 2019, 18:14
  #8 (permalink)  
 
Join Date: Apr 2000
Location: EGDC
Posts: 8,044
Use the RFM before you fly to check you have at least OGE power available at the expected temp/pressure/AUM at the LS.

Then deduct 5 or 10% of the MAUM indicated by the graphs - that will give you a thrust margin.

Finally do an in-flight power check within 5nm/500' of your LS to confirm you can get max power.

Land safely taking into consideration local wind effects.
crab@SAAvn.co.uk is offline  
Old 27th Aug 2019, 08:50
  #9 (permalink)  
 
Join Date: Apr 2000
Location: EGDC
Posts: 8,044
FB - your screenshot shows the same AUM calculated for AEO HIGE, AEO HOGE and Cat A VTOL - there should surely be a difference if it is about performance unless that 3650 Kg is at the edge of the graph?
crab@SAAvn.co.uk is offline  
Old 27th Aug 2019, 09:24
  #10 (permalink)  
 
Join Date: Feb 2006
Location: Germany
Posts: 846
Originally Posted by [email protected] View Post
FB - your screenshot shows the same AUM calculated for AEO HIGE, AEO HOGE and Cat A VTOL - there should surely be a difference if it is about performance unless that 3650 Kg is at the edge of the graph?
The one in good quality is a sample picture - which doesn´t really mean, all the figures must be correct - its just showing, where you find which information.

The screenshot with the low quality gives the correct numbers, which were for the time - Summer, 200 feet AMSL
Total weight 3078 kg
AEO HIGE 3700 kg (MTOW)
AEO HOGE 3700 kg (MTOW)
CAT A VTOL 3603 kg
OEI 30s HOGE 3378 kg
OEI 2min HOGE 3039 kg - amber - not yet possible
Flying Bull is offline  
Old 27th Aug 2019, 10:28
  #11 (permalink)  
 
Join Date: Apr 2000
Location: EGDC
Posts: 8,044
Thanks FB - that makes much more sense
crab@SAAvn.co.uk is offline  
Old 27th Aug 2019, 14:22
  #12 (permalink)  
 
Join Date: Dec 2006
Location: yes
Posts: 246
Originally Posted by HeliHJ View Post
Could anyone enlighten me with an “on the job” technique method for power checking before going into a landing site. I currently fly light SEP’s and curious as to how you go about it on a big bird.
For info, one method I have been taught:
25kts gnd speed
check power
add 15% for IGE
add another 15% for OGE
Your “power check” appears to be a “rule-of-thumb.” And as such, it’s not intended to be strictly accurate or reliable for every situation. For example. Imagine flying at a density altitude where the power required for 25 knots is nearly the maximum power available. In that situation, HIGE and HOGE would probably be impossible. A HIGE/HOGE determination has 3 components, power required, power available and power assurance. Therefore, your “rule-of-thumb” really isn’t a “power check”.

It’s all on the screen (AS-350 VEMD shown):




JimEli is offline  
Old 27th Aug 2019, 16:50
  #13 (permalink)  
 
Join Date: Dec 2004
Location: england
Posts: 972
Fly a Chinook....

Power.... Check....plenty of it...
pba_target is offline  
Old 27th Aug 2019, 17:30
  #14 (permalink)  
 
Join Date: May 2002
Location: "Deplorable but happy as a drunken Monkey!
Age: 72
Posts: 16,612
I drooped the Rotor RPM so low on an early "A" Model Chinook....the Generators dropped off line.

That was an interesting takeoff!
SASless is offline  
Old 27th Aug 2019, 21:31
  #15 (permalink)  
 
Join Date: Mar 2007
Location: Hobe Sound, Florida
Posts: 751
Ah: SAS is addressing the “ other “ power check. This is especially a subject for the medium/heavy pilots, who face operating with loads and the people who would put them on your helicopter. What does this stuff weigh? The pilot can do his due diligence with regard to the engines meeting spec power, but then be undone by incorrectly marked loads, or more often unmarked loads which come with a guess* as to what they weigh and various combinations of the same. Now, what sort of power check can one do in that case?
*And some people flat out lie.
JohnDixson is offline  
Old 27th Aug 2019, 22:59
  #16 (permalink)  
 
Join Date: Dec 2006
Location: yes
Posts: 246
Originally Posted by JohnDixson View Post
...
The pilot can do his due diligence with regard to the engines meeting spec power, but then be undone by incorrectly marked loads, or more often unmarked loads which come with a guess* as to what they weigh and various combinations of the same. Now, what sort of power check can one do in that case?
...


Given the appropriate performance charts, they can be ran in a "reverse" direction to determine the gross weight. However, very few manufacturers (and the FAA doesn't require them) provide the appropriate charts. Military helicopters and derivatives usually have the necessary charts. With enough information, an individual could construct what is needed (I have done this for several helicopters).
JimEli is offline  
Old 28th Aug 2019, 06:04
  #17 (permalink)  
 
Join Date: May 2008
Location: East of Africa
Age: 44
Posts: 894
All that is a paperwork exercise conducted before even getting into a helicopter-and therefor useless when actually flying...


The question was about a check when flying......

And the deal is:
Will I have enough power available with the fuel/load, temperature, altitude and space available I have NOW, and will I be able to take-off again?

There is no chart for that (unless in the military, flying with a crew of 3, 4 or more, where one has enough time and staff on hand to read through all that crap while doing your recce).

The majority of us Utility pilots fly single pilot, and have to fly in rough terrain.


That's where our "rules of thumb" come in handy...
hueyracer is online now  
Old 28th Aug 2019, 06:35
  #18 (permalink)  
 
Join Date: Apr 2000
Location: EGDC
Posts: 8,044
So you don't really know your AUM when you are flying then?

Surely you must have an idea of the likely pressure and temp you will be flying in during your day and can work out a best case and worst case scenario based on fuel and load?

Remember the seven Ps
crab@SAAvn.co.uk is offline  
Old 28th Aug 2019, 09:08
  #19 (permalink)  
 
Join Date: Jun 2002
Location: east ESSEX
Posts: 3,650
Crab,some of us are reminded about those every night....!!
sycamore is offline  
Old 28th Aug 2019, 09:37
  #20 (permalink)  
 
Join Date: May 2008
Location: East of Africa
Age: 44
Posts: 894
If you are flying in mountainous terrain, you will not know all details......

You will be able to calculate your weight at the time of arrival, but that's about it.

Wind situation up there is unpredictable, and so is the temperature.

Same with unknown LZ in the rain forest.... You don't even know the exact location-sometimes you just have a coordinate, and you know the recce team will be on the ground within a few km radius of that coordinate.

Now tell me how you are doing your calculations before the flight?

Especially in remote areas, with no weather forecast or reporting station within 1000 nm?


That's why Offshore pilots are usually unprepared when coming into the Utility world, as they are used to much better service around them... (let's not get into a debate about it again, Utility pilots getting into the Offshore world also struggle...)..
hueyracer is online now  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.