Ask The Pilot

[mjt57]

The RAAF only operates the CT4 with AVGAS. Everything else uses AVTUR.

What's the difference between the two? And why Avgas and not Avtur?

 

[AviatorInsight]

What's the difference between the two? And why Avgas and not Avtur?

AVGAS or Aviation Gasoline is commonly used in piston engines because of the higher lead additive to achieve a higher octane rating and is dyed according to octane. For example there is 100LL (Low Lead) which is blue, or if my memory serves me correctly, straight 100 which is green.

AVTUR or Aviation Turbine fuel is used in gas turbine engines and has a straw coloured appearance. Common types or AVTUR are JET A and JETA-1. Jet fuel is similar to kerosene. It has a higher flash point than AVGAS and so has an added safety feature in the event of an accident.

 

[mjt57]

Oh, never mind. I got the CT4 mixed up with what the Roullettes fly. ie. piston v turboprop...

Doh...

 

[jb747]

AVTUR, AVCAT, Jet A1 (and some others) are used in turbine engines. It's basically kerosene.

AVGAS is petrol.

 

[jb747]

I guess i should have specifically asked (the pilot / those in the industry) - any ideas on how long this is expected to ask?

None of us know, but the situation is apparently easing already. I was able to get the 196 tonnes that I wanted.

 

[docjames]

None of us know, but the situation is apparently easing already. I was able to get the 196 tonnes that I wanted.

Good news - don't want an extra stop to EU next week......

 

[lastrow]

AVTUR, AVCAT, Jet A1 (and some others) are used in turbine engines. It's basically kerosene.

AVGAS is petrol.

I think the problem in Melbourne was that the wrong fuel was delivered and fortunately the error was picked during routine testing. If I heard correctly what should have been AVTUR was AVGAS. If this fuel had been delivered and tanked underground the clean out could take a long time.

 

[mjt57]

None of us know, but the situation is apparently easing already. I was able to get the 196 tonnes that I wanted.

So we saw. Watched you departing MEL from the Melbourne Showgrounds today. Unfortunately the iPhone camera took a photo of what appears to be a gnat in the distance. Those with me commented on how big the A380 looks, and how slow it looked as you commenced your climbout.

 

[RAM]

None of us know, but the situation is apparently easing already. I was able to get the 196 tonnes that I wanted.

If only one could earn FF points on THAT fuel purchase....

 

[petercr]

Was that Caltex or BP? (but don't they have a 150lit limit?)

 

[whatmeworry]

IIRC a Captain from a LLC on a reality show, pulled out the company CC to fill up.

 

[Flashback]

IIRC a Captain from a LLC on a reality show, pulled out the company CC to fill up.

Easyjet IIRC?

 

[Boca68]

Easyjet IIRC?

An Easyjet CC?

Would have immediately done a fraud check on Stavro's CC

Anyway, back OT.

I believe, not totally reliable, that all airlines involved in the latest fuel issue at MEL, were told they could have 50% of their requirements. No preference given to local or long haul. But that only lasted less than 24 hours.

 

[flychrisfly]

Do engines need time to cool down after a flight before commencing another?

 

[jb747]

Do engines need time to cool down after a flight before commencing another?

They need time to cool before being shut down. 380 is five minutes, and 747/767 was three. When starting up again, you don't normally put fuel into the mix until the temperature is below 100ºC, but you'll get that just by motoring the engine for slightly longer.

So, to answer the question....no.

 

[AviatorInsight]

Do engines need time to cool down after a flight before commencing another?

Not really no. It's more common to have a limit for a minimum temperature prior to take off. After landing though, having a hot casing rapidly cool can cause rubbing so there is a cool down time. For the B777 it's 3 minutes. Very convenient when landing on 6R at LAX in the morning and vacating straight to TBIT onto the bay 3 minutes after landing.

 

[flychrisfly]

Not really no. It's more common to have a limit for a minimum temperature prior to take off. After landing though, having a hot casing rapidly cool can cause rubbing so there is a cool down time. For the B777 it's 3 minutes. Very convenient when landing on 6R at LAX in the morning and vacating straight to TBIT onto the bay 3 minutes after landing.

So engine speeds while taxiing will 'cool' the engines even if not at idle?

 

[serfty]

So engine speeds while taxiing will 'cool' the engines even if not at idle?

I think you'll find generally such a 6R landing with taxi to TBIT has a minimum taxi time (for LAX) - so the B777 only needs three minutes - contrasted to the A380's five.

With such a 3 minute taxi, I can envisage A380's having to wait at the gate, engines running for another two minutes before shut down.

 

[AviatorInsight]

So engine speeds while taxiing will 'cool' the engines even if not at idle?

Most of the time we will be taxiing in at idle power anyway. There is a lot of residual thrust from the GE90s. Unless we come to a complete stop then only minimum breakaway power will be needed but it's not enough to warrant a re timing of the cool down.

 

[jb747]

So engine speeds while taxiing will 'cool' the engines even if not at idle?

At idle the engine temps are about 300ºC, versus 700º or so in reverse. We're only concerned about the extreme temperatures. After landing, we can taxi at idle, even starting from stop if the taxiway is level (so not Melbourne). Even if we do need some power, it's unlikely to exceed 10% thrust. Even at idle, we're probably still generating about 12,000 lb of forward thrust.

The start time for the engine cool down period is the point at which idle is selected during the landing. So, that means that the outboards start the clock earlier than the inners, because only the inners are fitted with reverse. The upshot is that we can occasionally shut down the outers whilst still on the way to the gate. This modified timing can apply to any engine if we've only used idle reverse.

The only place where we regularly reach the gate and have to wait before shutdown is Dubai, where an exit off 30L at K8 or K9 drops you right at the gate.