Power check technique for twin turbines
 

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..

Two different things. One is for engine health the other a rule of thumb for calculating powerrequirement for a given situation.

skadi

:ok:
Thanks, pic was nearly unreadable on mobile phone..

skadi

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.

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

Thanks FB - that makes much more sense :ok:

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):
https://cimg6.ibsrv.net/gimg/pprune....87b3a42d67.jpg

Fly a Chinook....

Power.... Check....plenty of it...

I drooped the Rotor RPM so low on an early "A" Model Chinook....the Generators dropped off line.

That was an interesting takeoff!

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...

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:ok:

Crab,some of us are reminded about those every night....!!

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...)..

So you don't have maps with contours to help assess the altitude of the LS? Or google? Or local knowledge of the terrain? Or an approximate maximum altitude you might be working at?

Just the appropriate graph from the ODM for HOGE on a kneepad coupled with an OAT guage and the altimeter reading would be a pretty good start.

No 'rule of thumb' in flight power check is going to help you assess the wind at a mountain LS - you have to assume no wind assistance and plan accordingly.

PS, I'm not an offshore pilot nor ever wish to be:)

I can tell by your comment you also have never flown in certain remote areas....


Large parts of the rain forests in Africa are just blank spots on maps more than 100 years old-you simply can not get maps, period...

The camp I was in did not have internet access or electricity for the better part of 3 years.... Then came a generator... Followed by satellite internet...

Of course you get an idea on your power available.... But this is no training environment-if you screw up, you don't get a second chance... So if you miscalculated your power available on the approach, you might end up in the jungle with not enough power to climb out of the area again....... Now what do you do?

This is where those checks come into play.... Although they are called "rules of thumb", checking those things while doing a recce before landing always (always!) gave me the accurate information I needed to make a good judgment.....

It's up to any pilot to do whatever he wants.... I will continue doing those checks for the rest of my flying career...

So how do you ensure you are keeping within the WAT limits in the RFM?

You are correct that I haven't flown in darkest Africa but if you are operating in the same area for a while you must have an idea of the local terrain.

I'm not saying you shouldn't do your checks and I presume you make an allowance 'for the wife and kids' and err or the side of safety when flying into such sites.

Absolutely....

What I usually do (not saying this is the way it should be done) :

On arrival at the site, I talk to the pilot who has been there before (if applicable), and/or create a little exel spreadsheet with weights/altitude/temperature and range limitations...

This gives me a rough idea already....

In addition to that, I do my "checks" before going into the LZ as stated above.... And of course, on the Bell mediums at least, doing a power assurance check on a daily basis as a trend monitoring... We did not have an engineer on site for a while, hence it is even more important to know your aircraft....


Since my military flying days I made it a habit to always Brief myself (or the copilot if there is any) on the aircraft weight before each approach or departure as well (and the fuel status, and the altitude... And the density altitude.... And the temperature... And and and...).

In the real world flying some do everyday.....that is a very common occurrence.

A few examples....

You land on the Oil Rig and are given a Manifest showing numbers of passengers (using standard weights) and a Baggage weight (presumably weighed).

There comes Bubba dragging a Duffle Bag and carrying a suitcase and Tool Box.....in company with his brothers....all of whom look like the Incredible Hulk's. big brother.

You reckon they are "standard" weight....and all their kit weighs 20 Kilos each?


You land to pick up core samples of rock at a hilltop core drill.

How do you weigh that bit of cargo?

It is easy in a well structured environment to weigh passengers, cargo, baggage, determine the Temperature, Elevation, Wind, and distance to and height of obstacles......but not in the real world of utility flying.

You can weigh the aircraft by using the weight and balance information in the RFM and Aircraft Records, check the elevation and OAT, then reference the WAT Charts but after that it gets a bit ambiguous as to what you are dealing with sometimes.

Years ago, in Belize, a new army major took over at Rideau camp down south and having discovered that the Puma could be fitted with sixteen seats he protested very strongly that his unit were getting short changed and that the RAF weren't doing their job properly because our standard seat fit was twelve plus a winch. The OAT was often in the 90's and the humidity was often 95% so we really couldn't carry sixteen pax and any fuel to speak of (the HC1 only had an endurance of about 90 minutes from full tanks).

He decided to begin weighing every soldier before they were boarded and made a written record of passenger loads to present to OC RAF (and hence earned himself the nickname "bathroom scales"). The outcome was that the seat fit went down to ten because in fact we were being too generous in what we were already doing with the aircraft - the army had been very much under-estimating the weights of the average troop plus gear.

I had an "interesting" departure from that site, as a keen first tourist. We used to fly a group of soldiers plus a local policeman to a very small, disputed offshore island for "R and R" on most Fridays. The usual thing was to load the aircraft up with all the food and drink for their weekend in a very large aluminium "trunk" and then put a few buckets of ice in on top. Unknown to us, on this particular day they had loaded the ice far too soon before our take off and it had melted. Without emptying the melt water, they had kept on topping up the ice. By the time we lifted, the container was brimming and was a huge amount over the declared weight.

The "helipad" had been designed for a Westland Scout (far smaller & skidded u/c) and there was only about a foot of spare room fore and aft for the wheels of a Puma and none of it could be seen by the pilot once over it. It was raised by about five feet because the area was very boggy and criss-crossed with ditches hidden in long grass and was no place to try to put down a wheeled helicopter, even at the best of times.

I lifted to the hover and as soon as I had, I realised that this bird really didn't want to fly. I had no option to land back for fear of dropping a wheel off the edge of the pad, so I had to keep going....and going.. and going, scrabbling to find translational lift. The ammo dump was straight ahead; I remember staring at it for what seemed far too long. We did clear it, but only just and the Puma missed the trees beyond by a few feet. I think we all learned something from that. We found out afterwards that the soldiers had found great difficulty in loading the container onto the aircraft but didn't think to tell anyone that it was far heavier than normal.

Why do we continue to do this? For example, couldn't we demand governing bodies make manufacturers provide the required data in order to perform simple go/no go checks. just saying.

Sasless - you say in a structured environment it is easy to keep a handle on weights, having just given an example of an issue when rig flying - is the offshore environment not the most structured and safety conscious of all helo tasks?

Just keep in mind that we all gained our experience in different environments...

I am sure (although I don't know) that Offshore in the North Sea is over regulated, whereas flying offshore out of places like Sudan are still pretty much Bush operations....


It is difficult to understand someone's requirement to use a "rule of thumb" (because that is all he has got on hand where he is) if you are flying in the North Sea with all Bells and whistles, even with ground crew preparing your load manifest for you and delivering it to your cockpit with a steaming mug of Joe's!
(exaggerating for dramatic effect).

Offshore and utility as many know are comparable to, well nothing. The only comparable relation is that the guy wiggling the jiggly bits has a license in his pocket. Graphs must / should be used whenever / wherever but in some / a lot of areas these may not be feasible. We have that license to insure we do the best / safest job we can.

Many times I have used ever tool at my disposable in the offshore to insure I had sufficient power for ever regime of flight ( and there are many ) only to find out in flight that .... this sh!t ain't working. I have shot many approaches to the same rig with roughly same wind but on short final you realize the wind given was not accurate and you do not have the TQ to continue .... you abort. (See license in pocket)

I have used every tool in my tool bag to insure that I have the TQ to go from Sea Level to 5000' with a load of drill rod. You say "well I did this yesterday with same conditions 37 times" to find out that updrafts / downdrafts / (or lying drillers) have caused me to abort on short final. (Check license in your pocket)

Moral of my story, powerchecks yes, but we still have to use the license in our pockets as much the graphs in the books. Or, you may find yourself (possibly) looking for other employment.

Some of the finest and safest utility pilots I have worked with could struggle to find a performance graph in a RFM except for once a year. Some of the worst offshore pilots I have flown with could recite the RFM from the stem to stern but struggled with the jiggly bits.

My....how Standards have slipped!

Coffee?

A proper cuppa, Lad......Char....Chai....TEA!

I think they used to serve drilling mud when I was there!