Start up in cold weather: Helicopters

[peeush]

As a helicopter pilot, there are frequent instances when I need to start up on 'internal' battery in remote heliports. The issue crops up at lower temperatures (+15 degrees C or below) when the 'cranking' and initial acceleration of turbine isn't adequate resulting in high exhaust temperatures in some cases.

Here's the question:

Are there batteries in open market that can hold adequate charge to provide acceptable cranking even after prolonged parking in lower ambient temperatures and facilitate a flawless start (considering helicopters upto a weight class of upto 7000kg). If any, will these be safe to operate at higher temperatures of upto +50 degrees C.

Just that it doesn't go unsaid---We may exclude on board APU start option from the discussion.

[army_av8r]

About Tesla ? Industries Inc | Micro Power Units (http://www.teslaind.com/products-micro-power-units.php)

Not sure about the different sizes of these batteries. But, amazing start performance for light helicopters.

[Winnie]

We have two Tesla batteries in our Bell 214ST, and it cranks fine in -30°C temps (and colder). The batteries are self charging and self heating. We plug in an extensioncord and that is all that's needed. We have a separate Herman Nelson heater that we use to heat up the elastomerics of the running-gear.

I have flown Tesla batteries in Bell 206B and L3 helicopters, and the starts were incredibly fast and cool in both. Down to 11 seconds from introducing fuel to 58% on the Jet Ranger!

Anyway, fantastic batteries!

[dogle]

Before you rush out to buy new batteries, peeush, here's a tip which might just save your outfit some useful cash. I note that the problem arises at temperatures which shouldn't affect the battery performance too much, but only with onboard starting at remote heliports, where I presume there is no GPU to help.

Have someone check carefully that all connections in the onboard battery cranking circuit are, not just good, but perfect (that includes the contacts in any breaker/solenoid dedicated to that circuit, and is not quite as easy as it sounds).

Here's why: suppose f'rinstance that you have a 28.5 V starting motor which is drawing 50 A at full chat; if somewhere in the circuit there has appeared a tiny spurious resistance of 0.1 Ohm (that's way too small to measure with an ordinary multimeter) in some connection, it will 'drop' five of your available volts and the motor will only be seeing 23.5 V. Because a square law is applicable, that's over 30% of your cranking power gone.

Thus, a very little can matter a whole lot ..... this often-unrecognised problem is a great little earner for the battery trade .... lots of good batteries are needlessly scrapped.

A technician may be able to do a quick diagnostic check by measuring the voltage appearing at the motor terminals under (onboard!) starting load; if the result is positive (volts mysteriously getting lost) then ideally someone with the use of a good resistance 'bridge' (very sensitive measuring device) may be able to pinpoint the fault most swiftly.

(BTW, just a gut feeling, do you tend to get supersaturation conditions overnight at those remote bases?).

[hueyracer]

The temps do not seem to be that low to me….

How about replacing the battery?

Do you disconnect the battery during the night?
That helps most of the times..

If the heli is parked outside for several days without flying (or the immediate need for flying as in EMS): Take the battery out and with you into a room….

[paco]

A cold battery has to do twice the work with a third of its power, or maybe the other way round. Either way, take it out and keep it warm if you can.

Phil

[jimf671]

... ...

Have someone check carefully that all connections in the onboard battery cranking circuit are, not just good, but perfect (that includes the contacts in any breaker/solenoid dedicated to that circuit, and is not quite as easy as it sounds).

Here's why: suppose f'rinstance that you have a 28.5 V starting motor which is drawing 50 A at full chat; if somewhere in the circuit there has appeared a tiny spurious resistance of 0.1 Ohm (that's way too small to measure with an ordinary multimeter) in some connection, it will 'drop' five of your available volts and the motor will only be seeing 23.5 V. Because a square law is applicable, that's over 30% of your cranking power gone.
... ...

Good call.

This is a problem for all low voltage systems. It doesn't matter whether it's aircraft, cars, trucks or segways.

On road vehicles, the usual way of checking is to measure the volt drop while cranking. This examines your worst case conditions and gives a useful measurable voltage that means something.

You have to examine both the negative line and the positive line to the starter since both sides of the circuit have resistance that is costing you voltage. Learn where every millivolt is going. (Check the generator lines during high charging demand while you are at this!)

It is typical to find connections and switches costing several hundred millivolts each if they have been regularly exposed to cold and damp. Obviously, that soon adds up to a significant voltage across the entire system. If cleaning connections can drive down volt drops to tens of mV at each one then you are getting somewhere. There may be a volt drop table available for your aircraft.

Where you draw the line between cleaning and replacement depends on what the maker and regulator have to say on the subject.

Wire size and crimp faults are other things to think about. If a section of wiring has been replaced then it is possible that an error has occurred that will increase voltage drop.

Always suspect any earthing braids or wires between units and check volt drops across them.

[John R81]

What helicopter?


Being based in the UK myself, most of the year my starts are below +15c.My EC120 is not flown every day but at least every 4 in winter and most days in summer. No GPU used unless we have a problem starting, and I don't carry a GPU to land away. I haven't had a problem with either of 2 EC120s unless (1) battery not fully charged; or (2) cells dead in the battery; or (3) dirty / lose / corroded connections.


I have also seen problems with EC130 earth cable "wearing through" (eventually breaking in flight) which first manifested as reduced starting performance.


I have also experienced dirty connections causing voltage drop, as noted above.

[ShyTorque]

Me too wondering about this. An external power start is a rare treat for the aircraft. It's below +15 for much of the year and we don't have problems unless someone has been using the battery for too long on the ground.

[chopjock]

pee
If you are stuck away from base and you don't have an external battery, have you tried winding the rotor head up first? The way I do it (if needed) is turn the rotor by hand as fast as you can then jump in and press the starter. Or get someone else to help you.

[ShyTorque]

Really? Why not just tow the aircraft behind a Land Rover and get it to autorotate?

The Germans used to do this behind submarines. The pilot used to point out enemy shipping. Then if he saw danger, the sub would immediately dive......

Nurse, my tablets please! ;)

[EN48]

Here is a possible easy and relatively inexpensive solution, but it depends on what the definition of "remote" is. Weighs 1.5 lbs and requires AC power. Will keep the battery fully charged and somewhat warmer than would otherwise be the case (but its not intended to heat the battery). Have used one for many years and recommend it highly. http://www.power-products.com/Datasheets/Activator_282_Brochure_Flyer_EN-P6001-1001.pdf


Here is another possible solution, but may not meet your "no apu" requirement, and not so inexpensive. I have seen these at HAI but have never used one: StartStick - Aviation Battery Systems LLC (http://www.aviationbatterysys.com/startstick/)

[helicopterray]

+15C is not cold. You have other issues with your electrical system.

[peeush]

Thanks all for the inputs, guess some will help me find the right problem. Though, I think getting the terminals clean and getting the circuit check for the 'leak' is the first thing I'm going to do.

Thanks again.

[helimo]

Can someone please explane why there is an increased danger for hotstart at low battery power and/or in cold weather ?

[paco]

Simply because the battery is not powerful enough to blow cooling air through the engine - the battery is required until the engine reaches self-sustaining speed.

Phil

[John R81]

I am guessing that a jet turbine engine pulls in more air than is needed for combustion because the extra air keeps the fuel-fed burn away from the sides of the combustion chamber and therefore reduces the heat load on the expensive shiny bits. When the battery is down on power the starter generator does not reach the required speed so the volume of air pulled into the combustion chamber is below the designed flow and the burn is not kept away from the expensive bits, which then overheat and stop being shiny.

You can probably tell from the technical language that I own / drive them but I don't build or fix them. Hopefully someone will be along shortly to provide a better explanation.

[Hiller Hornet]

Hi Winnie thanks for the info on the Tesla batteries sounds like a great idea.
Do you know if they are approved for use in the Bell 206 helicopters? I could not find any info on the web site about appoval basis??

[Winnie]

The company I work for in Canada was looking to do an STC on it, don't know how far that has gotten, but the tests where done in 2011, and the 214ST uses them now.

Cheers
H.

[nomorehelosforme]

You guys up north must know more about cold starts and white outs than most at the moment, especially with a Polar Vortex heading your way( whatever one of those is!)

Fly safe.

[unstable load]

I am guessing that a jet turbine engine pulls in more air than is needed for combustion because the extra air keeps the fuel-fed burn away from the sides of the combustion chamber and therefore reduces the heat load on the expensive shiny bits. When the battery is down on power the starter generator does not reach the required speed so the volume of air pulled into the combustion chamber is below the designed flow and the burn is not kept away from the expensive bits, which then overheat and stop being shiny.
In a nutshell.:ok:

[MightyGem]

Am I the only one who thinks that perhaps the OP meant minus 15 degrees? I can't really think of plus 15 as being cold.

[AnFI]

+15 is cold in (OP's) India and also in F ... but he does say C. Otherwise it sounds suspiciously close to ISA'a standard sea level temperature :confused:

One may be able to start in exceptionally cold conditions but it does not mean it's ok since it can damage components which become dimensionally changed (tight):eek:

[paco]

That's why you start the engine every couple of hours in Arctic conditions.

Phil

[thechopper]

or keep it in a hangar in even colder environs:sad:

[vfr440]

Northern Quebec/Labrador, SEBJ project, fly-survey of Great Whale river, Bell 206, 1974/5. :ugh: Hmmm - no hangar within 500 miles.http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/boohoo.gif Just put the covers on (all of them) and take the battery to bed - no, seriously. http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/pukey.gif


Why do you think I returned to the sandpit! http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/thumbs.gif - VFR

[Tynecastle]

Or the 61's and 212's in the Western Arctic, -40 C/F. No hangar, just covers, Battery blankets, and a good Herman Nelson Heater.
When Herman went u/s you were definitely AOG

[vfr440]

http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/smile.gif http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/smile.gif

[AnFI]

Tanis Aircraft Products - Aircraft Preheat Systems (http://www.tanisaircraft.com/RotorwingPreheat.aspx)

does it work for you?

[fijdor]

Tanis heaters are great, Add to it a electric batterie blanket, winter covers and your in business. Don't need anything else. We use that system on Astars and B205s up in Northern Canada and it can get cold there let me tell you.

JD