PDA

View Full Version : For Those Interested


Saintly
19th Jun 2018, 12:48
Hi everyone,

First of all apologies if I have put this in the wrong area of the forum, I wasn't sure where to put it.

This aircraft came into Perth on the 16th of June. Fast forward to the take off...the engines are smokers:

https://youtu.be/LNtBvl4pxDk

Cheers.

Capn Bloggs
19th Jun 2018, 12:57
Those idle-at-500ft-landings are a bit dodge...

And the mixture! Jaba, have a talk to them, will you? The No 2 looked better tuned to me.

wheels_down
19th Jun 2018, 15:55
Why is it here?

Ascend Charlie
20th Jun 2018, 01:02
Did Igor leave the choke out?

tail wheel
20th Jun 2018, 01:39
Needs a new set of piston rings! :}

troppo
20th Jun 2018, 01:54
You're all wrong.
It is a top secret low level Chemtrail experiment on unsuspecting Australians.
Just watch. Y'all gonna start speaking faster, walking faster and start breeding outside your family gene pool

Slippery_Pete
20th Jun 2018, 06:11
Where is Geoffrey Thomas when you need him?

He would get to the bottom of it.

Capt Fathom
20th Jun 2018, 06:53
Latest Qantas innovation for the Perth market.

Saintly
20th Jun 2018, 08:39
Sounds like a loud turboprop too when it taxis. Most turboprops are.

megan
21st Jun 2018, 00:35
That ain't smoke, this is smoke.

https://cimg2.ibsrv.net/gimg/www.gmforum.com-vbulletin/1076x656/0541868_34a9b75d088670e6eef05e4a060f59e0907f7458.jpg

Kranz
22nd Jun 2018, 02:18
^^ out of interest, isn't that a little bit of an early call for "gear up"?

C441
22nd Jun 2018, 02:58
^^ out of interest, isn't that a little bit of an early call for "gear up"?
Not when there's a photo to be taken.
Reminds of an F28 in Tennant Creek a year or thirty ago!! Not quite as smoky though…..
https://cimg5.ibsrv.net/gimg/www.gmforum.com-vbulletin/276x185/tennant_creek_takeoff_5de528d9c3b43e4a2c97e67db169ee5a4e8dd0 37.jpg

topdrop
22nd Jun 2018, 03:08
That looks like BH's photo of F28. I have seen similar shot of his of an F27 at Tennant Creek with early gear up - the props are only just clear of the tarmac - a little bit of sink as gear came up!!.

On eyre
22nd Jun 2018, 03:45
Yes Topdrop - BH has some brilliant stuff from that era. Those were the days.

C441
22nd Jun 2018, 05:00
That looks like BH's photo of F28.
Yep, and from memory he had a coupla days off afterwards as a result of a "minor ear infection" rendering him temporarily deaf!

Those were the days.
He was among a number of great Flight Service operators in Gove, Tennant, Darwin, Alice and, I'm sure, numerous other out-stations.:ok:

Some of the blokes from Alice Tower in the early-mid 80's join us for our Tillair/Chartair reunions; it would be great to get a few more of the ATC/FSU team together….might need a few days off afterwards though!

Saintly
23rd Jun 2018, 04:02
I remember Skywest and they used to bring up their F50 landing gears quite early after takeoff if memory serves me correctly.

swh
23rd Jun 2018, 07:14
I remember Skywest and they used to bring up their F50 landing gears quite early after takeoff if memory serves me correctly.

Good airlines tend to retract their gear after takeoff, the takeoff run is longer and causes more wear if done before hand.

Traffic_Is_Er_Was
23rd Jun 2018, 11:36
I remember watching the An12's depart BNE on their fish charter runs. Similar smoke trails disappearing out over Moreton Bay using the curvature of the earth to gain altitude. I reckon Russian ATC worked by looking out the center's windows and making sure the smoke trails didn't cross.

BewareOfTheSharklets
26th Jun 2018, 09:22
Where was it arriving from/departing to?

Capt Fathom
26th Jun 2018, 12:01
Where was it arriving from/departing to?
The Sky! :E

lo_lyf
26th Jun 2018, 12:48
So what causes a turbine engine to leave a trail of black smoke? We know that when a piston engine blows black smoke its running too rich.
Doesn't a turbine engine follow the principles of lean-of-peak. As in, its got way more air than required to burn the fuel, so shouldn't all of the fuel burn cleanly?

megan
27th Jun 2018, 08:17
So what causes a turbine engine to leave a trail of black smoke Combustor design is complex, and in the early days the computer systems were not available to do the number crunching or flow simulations. An improved combustor was introduced on the Allison T56 engine fitted to P-3 which reduced smoke.

http://www.dtic.mil/dtic/tr/fulltext/u2/a227750.pdf

JohnMcGhie
28th Jun 2018, 07:47
So what causes a turbine engine to leave a trail of black smoke? We know that when a piston engine blows black smoke its running too rich.
Doesn't a turbine engine follow the principles of lean-of-peak. As in, its got way more air than required to burn the fuel, so shouldn't all of the fuel burn cleanly?

In a word: "Fuel Cooling". On my Airforce Engine Mechanic's course, I was told:

In the early days, Rolls Royce held the patents on most of the alloys capable of holding their strength in the high temperatures developed in the hot section of a turbojet engine. Other manufacturers, particularly the American ones, had to make do with lower-temperature-limited alloys. To prevent the engine melting its turbine blades off, they were "fuel-cooled" at take-off by injecting sufficient fuel to develop a massively rich mixture. Hence the "signature" soot trails.

With the development of better alloys, ceramic coatings, and hollow turbine blades allowing cold air to flow through them (and in the latest versions, to be pushed out of the blade leading edge, forming a protective layer of cold air over the blade) engine manufacturers have been able to raise their turbine inlet temperatures, and hence, to lean their mixtures out. A lot!

And of course, as Megan says, improved combustor design enables the fuel to be more completely vaporized and thus burned before entering the turbine.

amberale
28th Jun 2018, 13:51
The Caravelle that used to leave Brissy to the east was the dirtiest regular operator I saw.
ANA with #2 on fire was worse.

megan
29th Jun 2018, 02:36
In a word: "Fuel Cooling". On my Airforce Engine Mechanic's course, I was told Youse was told wrong John. ;) The only turbine I've heard of that uses fuel rich for cooling is the theoretical turbo rocket engine where combustion temperatures are of the order of 3,500C, versus 1,800 to 2,000C in your regular turbine.

The pollutants found in the exhaust gases are created within the combustor. Use of an airspray nozzle to inject fuel, which carries a proportion of the primary combustion air with the injected fuel, aerates the spray, reducing both carbon formation and exhaust smoke. Other nozzle types produce localised fuel rich concentrations and increase pollutants. There are four main pollutants which are legislatively controlled; unburnt hydrocarbons (unburnt fuel), smoke (carbon particles), carbon monoxide and oxides of nitrogen. The principal conditions which affect the formation of pollutants are pressure, temperature and time. With all other things being equal, the temperature of the gases impinging the turbine is controlled by what percentage of the compressor output is used for combustion compared to that used for cooling. Better turbine blades allows a reduction in the percentage devoted to cooling air, thus increasing temperature and efficiency.

A good book on the subject.

http://airspot.ru/book/file/485/166837_EB161_rolls_royce_the_jet_engine_fifth_edition_gazotu rbinnyy_dviga.pdf

josephfeatherweight
29th Jun 2018, 14:32
That's a fantastic book, thanks for posting the link, Megan.

JohnMcGhie
2nd Jul 2018, 12:19
Youse was told wrong John. ;) The only turbine I've heard of that uses fuel rich for cooling is the theoretical turbo rocket engine where combustion temperatures are of the order of 3,500C, versus 1,800 to 2,000C in your regular turbine.

I sit corrected: thanks Megan! I can't think why I didn't look that up in 1966 when I was told it, I hate being wrong :O ...

Mind you, I was training on cutting edge technology: Halford H1 (later and more widely known as the de Havilland Goblin (https://en.wikipedia.org/wiki/De_Havilland_Goblin)) out of the De Havilland Vampire, and the Rolls Royce Avon in the Canberra... OK, they had been in service for more than ten years by the time I got there: but I hadn't :-)

megan
3rd Jul 2018, 02:25
I hate being wrong Not you wrong John, was your lecturer. The JT8 was a smoker originally and new combustors were successfully trialled on a 727, similarly with the Olympus on the Concorde, the prototype was a smoker but new combustors were introduced.