water methanol whats it for?

[geisha girl]

In relation to garrett engines.

[fruitbatflyer]

I will not pretend to give a scientific or even very technical answer but basically if you brew a mix of demineralised water and good old metho, the metho is held nicely in suspension in the water (as an aside, if you get water contamination in your car fuel tank, a bottle of metho may clear it).
Now, when high power is needed, as at takeoff on a hot day or at a high elevation, squirt the watermeth mix into the compressor section of your little turbine engine working so hard. The water adds density to compensate for the hot/high conditions, but on its own could put the fire out in the combustion section. However, the metho, if in the right ratio, allows the whole brew to burn, vaporising the water part of the mix after it has done its job. This denser 'charge' gives a power boost while not exceeding EGT or TGT limits, as would be the case if you did something silly to boost the power, like for example use avgas (it has happened and while the initial power boost is quite impressive, it well and truly melts the turbines, so make sure the methmix is correct for your engine!).

[MoFo]

Excellent reply. Couldn't have done it better.
The old F27 with the pommy prehistoric engines used it too. (was it the Rolls Royce Dart?)

[Ausatco]

Yes, MoFo, they were Darts.

There was also a "fuel trimmer" spring loaded toggle switch with an accompanying indicator - can't remember what units it showed, maybe just numbers 1 to 5. At commencement of engine start they had to be at at one end of the scale (can't remember which) and as the engines lit up had to operated to prevent TGTs exceeding limits. FO would do that, Captain would have his hand on the high pressure fuel cocks, ready to shut them off if TGTs got out of control. In northern WA summers we often got close (950deg C was the limit on start-up, I think). Can't recall aborting a start, but can recall ordering water-meth replenishment with the fuellers at TOD.

All very hazy - 32 years ago, and I'm not aircrew. Was on airline attachment with the then MMA for 6 weeks as part of ATC training. They don't do that sort of thing any more - more's the pity.

AA

[olderbutyzer]

Water methanol (methmix) also used in the HS748 aircraft - Rolls Royce Darts again.

[ironbutt57]

quite sure the alcohol content is for freezing protection lots of jets and recips used it as well

[Desert Flower]

Ummm, don't know about the alcohol content being used to prevent freezing. A lot of small corporate jets & turbines use an additive called "Prist", which is an anti-icing anti-fungal compound.

[18-Wheeler]

Ummm, don't know about the alcohol content being used to prevent freezing. A lot of small corporate jets & turbines use an additive called "Prist", which is an anti-icing anti-fungal compound

AFAIK, Prist is only for the anti-fungus stuff.
Agree that the methanol is for anti-freezing, though as it soaks up the heat of the inlet air it also gives a good power boost. Try a Garret with pure water only and there's a BIG difference.

[ironbutt57]

prist is a fuel additive which is anti fungal/freezing used in small turbine engines not equipped with their own fuel heating system as on earlier bizjets using the ge cj-610 engines and a few others i believe water methanol ratios 60/40 vs 70/30 were used on different garret powered airplanes as well...you may notice the minimum oat for operation varied with this ratio..yes the engine performance would definately be affected by this ratio, and never heard of an approved means to use pure water...not saying it does not exist anyway sure gives a good kick in the butt when it fires....

[Deaf]

Something to consider is that (in Oz) Methylated Spirits does not contain any methanol (Methyl Alcohol or CH3OH). It is ethanol (Ethyl Alcohol or C2H5OH) with pyridine added to make it taste bad.

Years ago it was ethanol with some (5 -10%) methanol added but the cost of alkies going blind was too much.

[Hugh Jarse]

GG, Water Methanol is used to recover engine power at high ambient temperatures or high altitude airfields.

High ambient temperature results in a reduced air mass flow through an engine. Fuel flow must be reduced, in proportion, to avoid excessive turbine inlet temperature (TIT), and so engine power is reduced.

Injecting water alone into the compressor would cool the air by evaporation and increase the mass flow, so reducing the TIT. Maximum power could then be restored by movement of the power lever to increase fuel, but if the water flow ceased there would be an immediate over-temp at the turbine. Another disadvantage of pure water is that it freezes at flight temperatures (as mentioned in previous posts).

However, by adding a proportion of methanol (a fuel) to the water, the power may be restored without extra movement of the power lever. The methanol also acts as an anti-freeze for the water.

It's usually supplied to the engines at between 9 and 18psi.

Hope this helps, GG.

[ironbutt57]

some installations eg. allison 501...power recovery..back to 4000hp

tpe-331 on metroliner power augmentation 110% torque

some recips r2800 comes to mind....anti-detonation when superchargers working high bmeps during take-off

lots of applications, but the booze content is there for anti-icing as well..

[Bozzo]

Have to agree with previous posts stating the "meth"part was to prevent the freezing of the water rather than flaming out of the engines.

On the HS748 with RR Darts the H2O/Meth system would basically guarantee ISA atmospheric conditions (from the engines point of view) up to a density altitude of around 4500ft.

The standby system gave the best of both worlds: H2O/Meth performance without actually using it.

[Grivation]

Can someone please explain why the TPE engines are allowed the extra 10% torque with the CAWI working.

[Dale Harris]

Grivation, the Metro manual I have doesn't give a 10% increase in normal operation. It restores power you otherwise wouldn't have due to hot and high considerations. It does allow an increase in torque in the engine failure mode, i.e. the operating engine is allowed the higher limit, for a short time or until the water /meth is used. I think. :D :D I'll have to actually check it one day.............

[Grivation]

I thinks you're right with the -3 engines on the earlier Metro's. The -10/-11 engines have a 5 min 110% TQ limitation for use during wet TKOF's (normal ops).

Just wondering why? I always thought TQ was a mechanical limitation so can't understand why CAWI would change things.

[Hugh Jarse]

Griv, I think it's just a matter of how it's presented to you in the A/C, ie whether the SRL computers 'adjust' the EGT to display below limits or whether you see an "overtorque" situation on the torque meters.

Power Aug is a completely different kettle of fish to W/M in the fact that it permits "overfuelling" (for want of better words) of the good engine in an asymmetric condition when the takeoff would have been temperature limited. This is done by opening a fuel enrichment valve in both engines when it is 'armed'. In the J32, the signal to the EGT gauge was reduced by 19deg c. In the event of an engine failure, the power on the live engine would be increased until the EGT reaches the redline, then the TTL computer would operate to limit the EGT.

You pay a penalty however. From an engineering standpoint it costs you 4 engine cycles and 50 hours time for each hour Power Aug was used.

[ironbutt57]

The "overtorque" is allowed for wet operations..gearbox is actually good to 130% but at higher ambient temps two engine ops are permitted to 110% wet for 5 minutes...the garret installation is indeed certified as a power augmentation, ans is referred to as such in the afm...

[SmallGlassofPort]

Griv, the Metro 23 is certified to 110% trq wet or dry. The limit does not change at all when the water meth is switched on.
100% trq is max continuous power, and you may exceed this figure up to 110% for 5 minutes.
The engines can achieve 110% 'dry' in cold conditions, and this limit is commonly used for take off, baulked appr/landings etc

Hope this helps!

[gaunty]

A bit of Juniper Berry juice always helped with some crushed ice shaken not strirred.:D

[AN LAME]

You pay a penalty however. From an engineering standpoint it costs you 4 engine cycles and 50 hours time for each hour Power Aug was used.

You do pay a penalty from an Engineering viewpoint - a hell of a lot of the Engineers exposed to Water Meth constantly died before their time.

[SmallGlassofPort]

AN LAME,
Could you please give a little more info on your last statement?

I managed to swallow a decent size mouthful a coupla years ago... Whilst the groundy was refilling the CAWI tank and I was conducting a walkaround, the ever faithful FO decided to cycle the flaps. As the groundy fell from the wing with the trigger pulled I was in the wrong place at the wrong time.

Experienced symptoms later that night but all good again next day....

[AN LAME]

I'll try and get some more indepth info, but long term constant exposure, along the lines of Mobil Jet II( a la BAE 146 fumes), has knocked off a large number of LAMEs and Engineering staff over the years. I wouldn't think a mouthful who cause any lasting harm.

[gaunty]

AN LAME

The effects of Methyl Alcohol are fairly well known, I am intrigued by your comments.

I would not have thought that the fumes associated with "fuelling" would not have been all that 'voluminous' given the quantities involved.

Having said that they said the same about Prist (DEGMME) which is pretty serious stuff;

Health Hazards
Acute— Diethylene glycol monomethyl ether (DEGMME), the primary ingredient of Prist Hi-Flash aviation fuel additive, is an eye and mucous membrane irritant, a nephrotoxin and central nervous system depressant.
DEGMME can be absorbed through skin in toxic amounts when contact is extensive and prolonged; it is toxic by skin absorption. And it may cause pain and transient injury to eyes.

DEGMME may cause irritation to the mucous membranes. Due to the low volatility of this material, it is believed to present no unusual hazards from inhalation when handled at room temperature.
The oral toxicity of DEGMME is low.

Chronic— Fetal development abnormalities and effects on fertility have been reported to occur from prolonged ingestion by rats, mice and rabbits.
For additional information, please consult the MSDS for this product.



But like most hazardous material if handled properly is not a problem.

Do you know what they died of or if there were any studies conducted connecting the Meth with their death.??

And were there any other additives beyond Methyl Alcohol in the mix.

Our street people are known to drink the stuff straight for some time before they succumb???

[AN LAME]

Gaunty

As I said I'll try and get some more info. But my understanding is that it is from direct contact, not fumes, over a long period. It looks like you're more up to speed on it than I in any case.

[ITCZ]

SmallGlassofPort is correct

The -12 Garretts fitted to the some (better) Metro 23's are limited to 110% torque and 650 degrees EGT as max power, 5 minute limit, 'wet' or 'dry.'

Max Continuous is 100%, 650 EGT.

In both cases the EGT limit is reached first when not using water meth power augmentation (CAWI - continuous alcohol water injection) when OAT is about 30 or better, if my memory serves me correctly

Northern metro drivers would rarely see a low enough ambient temp to enable above 100% 'dry power' (ie no CAWI - water/meth injection). The 650 EGT limit would be reached first. Many of the topend boys who gained their first turbine/multicrew experience on M23's erroneously thought that 110% was a 'wet' or CAWI takeoff only situation as a result. This was only due to rarely seeing an ambient temp below 24 OAT.

Also seem to remember that the EGT limit was protected by the Single Redline Computer (SRL) operating a fuel bypass, whereas it was possible to exceed torque limits with a hamfisted operator.

Emergency power was available for abnormal operations only, by operation of a toggle switch on the power quadrant for -12 garret metros. This 'dropped' the sensed EGT by 20 degrees, enabling the engines to be run effectively at 670 degrees EGT before the SRL started bypassing, providing power to make gradients when one engine inop. This was to be activated if one had failed and if climb gradients needed to be met.

In low ambient temps (ie lower density altitude), CAWI added no extra capability.

Metro 23's had two interconnected CAWI tanks that held about 16 USG of fluid. This was usually enough for one application on takeoff and a second application in the landing climb. A normal (two engine) departure would use about 5-6 USG in three minutes, if it was switched off at or around 400 AGL.

The water meth required special handling as methanol is a poison as well as an alcohol. It could be dangerous in one contact as well as in repeated exposure -- should not be handled without eye and skin protection. Certainly don't try getting the siphon happening by sucking on one end of the tube!

[Deaf]

Hazards of Methanol

It is not extremely dangerous with a LD50 for rats of 5.5 gm per kg. (ie the lethal dose for 50% of rats) and rats are similar to people. the sg is ~.8 So a 285ml glass would contain ~228 gms and drinking two of them 570ml or ~456gm would give an 80kg person a 50/50 chance (but would probably go blind if they survived)

There are are problems with long term exposure for lower amounts also.

Regarding our street people methylated spirits have not contained methanol for many years for these reasons - see my previous post in this thread.

[AN LAME]

http://www.methanol.org/pdfFrame.html

http://www.epa.gov/opptintr/chemfact/s_methan.txt

Doesn't go into specifics of long term exposure. I'll try and get some more info from another source. Further anecdotal evidence from Engine LAMEs suggsts that towards the end of it's use at Ansett and Kendell it was handled with full body aprons, gloves, face masks etc. And it is regarded by many as the prime suspect in a number of Leukemia deaths.

[SmallGlassofPort]

Thanks Mate, most interesting.... and concerning

[bitter balance]

Thanks for the data AN Lame. The EPA document would tend to indicate the extremely low amounts absorbed through the skin or by vapours would be 100% metabolised. I can't see the long term exposure risk here, certainly not in the quantities we are talking about. Maybe the full body suits were as a result of OH&S requirements at Ansett? I would have thought Lames were exposed to much nastier materials than Methmix.

Methanol is obviously nasty in large quantities. To receive a lethal dose from a 50/50 Methmix you would have to doing something very wrong!

[Hugh Jarse]

Section 3 - Hazards Identification, Including Emergency Overview
METHANOL

--------------------------------------------------------------------------------
Health Hazards Acute & Chronic: CAUSES EYE AND SKIN IRRITAION. MAY CAUSE ANESTHETIC EFFECTS, LIVER EFFECTS, BLINDNESS, ACIDOSIS. MAY CAUSE NAUSEA, WEAKNESS, TEMPORARY CNS DEPRESSION, LOSS OF CONSCIOUSNESS, BLINDNESS, ABNORMAL KIDNEY FUNCTION, DEATH.

Signs & Symptoms of Overexposure:
IRRITATION, TEARING. BURNING SENSATION, DRYING SKIN, DEFATTING, DIZZINESS, NAUSEA, VOMITING, DROWSINESS, HEADACHE, FATIGUE, CONVULSIONS, UNCONSCIOUSNESS, DEATH, BLINDNESS, SWELLING OF EYES AND REDNESS

Medical Conditions Aggravated by Exposure:
INDIVIDUALS WITH PRE-EXISTING DISEASES OF THE EYE, SKIN, RESPIRATORY TRACT, LIVER, KIDNEY, CNS MAY HAVE INCREASED SUSCEPTIBILITY TO THE TOXICITY OF EXCESSIVE EXPOSURES.

LD50 LC50 Mixture: PRODUCT'S LD50 (ORAL RAT) WAS NOT STATED

Route of Entry Indicators:
Inhalation: YES
Skin: YES
Ingestion: YES
Carcenogenicity Indicators
NTP: NO
IARC: NO
OSHA: NO
Carcinogenicity Explanation: METHANOL HAS BEEN REPORTED TO CAUSE BIRTH DEFECTS IN RATS EXPOSED TO VERY HIGH CONCENTRATIONS (20,000 PPM), PER MSDS.

[Swear_in_GIN]

Heard an urban myth about 8 years ago in Canberra - someone had a car with a water washer on the headlights. Re-routed said waterline to the carburettor, and filled the headlight wash bottle with water-meths. Want and extra bit of boogy in the car? Just hit the headlight washbottle button!

SiG.

[the wizard of auz]

A small question for ITCZ, what the hell is a landing climb?.
I thought us mustering pilots were the only ones that did that sort of stuff.

[Sqwark2000]

I'm with the Wizard of Auz on this.....

I have heard/read this term "landing climb" a couple of times recently for the first time.... I have assumed it is similar to a missed approach or touch & go where one makes an approach to land but for wot ever reason discontinues the landing and proceeds with a missed/balked approach (climb)

Could someone confirm this for us and is this "new" airline terminology??

Cheers


S2K

[ITCZ]

Its not airline terminology, and it certainly isn't new! :)


CAO 20.7.1B sections 9 and 10, see

http://www.casa.gov.au/download/orders/Cao20/200701b.pdf

But I will admit that I picked the wrong term of the two. Approach Climb was the one where Water Meth could be used to make up performance. Sorry! :D

Basically "Approach Climb" is section 9 and refers to a missed approach in the approach configuration with one engine inop. In the metro this would be (memory here) Flaps 1/2, Gear Down, speed levers high, when the missed approach was initiated then the aircraft cleaned up to make the gradient.

"Landing Climb" section 10 is what we would all call a go around, all engines operating, from the landing config, i.e Flaps Down (full), Gear Down.

Section 9 would require that a Metro 23 be capable of making a 2.1% gradient or better in the missed approach with one inop.

In the hot and high aerodrome case, this may require CAWI with Reserve power. Again, three Regulated Landing Weight charts could be produced by the Fairchild performance program to calculate this with normal (dry) power, CAWI selected on missed approach, or CAWI on missed approach plus Reserve once exhausted.

Also note that if you were at max landing weight for the conditions and attempting to get in via an instrument approach, you would probably need to raise the MDA/DA, or raise your commital height in a visual approach.

The 2.1% gradient that section 9 asks for won't keep you above the 2.5% + 100' obstacle clearance requirement that the Missed Approach Procedure is designed around.

The quantity of CAWI required for the Approach Climb was less than that required for a EFATO. It was marked on the CAWI quantity gauge as a red triangle, and was about 4 USGal (memory again).

[John Eacott]

Water meth injection is also used on the Bell 206L, the original with the C20 engine. IIRC, 3 gallons carried in a stainless steel tank in the boot, and filled with a 1 part alcohol/2 parts water mix. Distilled water is required, and O-M-232d grade A meth.

Since the 206L is seriously underpowered, water meth injection is used on take off up to 52 knots, not below 738C TOT, monitoring to maintain <820C max TOT.

Fun part could be the "torsional oscillation" (Flight Manual term) that ensued if it wasn't introduced properly. ie the helicopter would bounce up and down as the engine & transmission tried to cope!