PDA

View Full Version : Catania & Baggage


Shamrogue
3rd Sep 2007, 10:39
Hi,
On a recent trip to Sicily. We departed from Catania with all baggage (for the whole a/c)being left behind. Our a/c was an MD83. We were advised that our bags were being left behind because the temp outside was 38C and therefore all baggage needed to be left behind.
I must admit I found this odd as I'm sure CTA regularly achieves daytime temperatures of 38C and above.
I would love to get a technical answer to this. Is this norm?
Regards and thanks
Shamrogue

Yer Man
3rd Sep 2007, 14:07
Shamrogue,

It is a law of physics, that air gets less dense when hot and therefore as temperatures rise aircraft get less lift. Any aircraft will have performance charts for a particualr runway and as the temeperatures rise the aircraft will be able to lift less of the maximum take off weight from that runway.

Then depending on the lenght of the sector to be flown, the crew may have a choice to make to either reduce the payload or ulpift less fuel and tech-stop en-route.

Shamrogue
4th Sep 2007, 08:40
Yer Man,

Good stuff. Yes indeed the laws of physics. This is where I'm trying to get a wee bit more technical in the answer.

Catania's Runway is 8727 feet long, it's elevation is 43 Ft. The next sector was from CTA to DUB. (our flight). OAT was 38C.
Our a/c MD83.
Now I suppose my real question is, can the MD83, come off that runway, in that temp, with full pax and baggage plus fuel.

And the reason I ask, is to get rid of the conspiracy theorists and the "hurlers on the ditch".
If ye can shed further light on this I would really appreciate it.
Thanks yer man.

Slan
Shamrogue

groundhand
4th Sep 2007, 09:10
An MD83 with a full passenger load, especially if majority were adults with few children, has no hope of taking a full bag load as well on that sector in those temperatures with little or no wind.

I don't have a DCS system available nor the aircraft weights etc. to work the details out but know from experience that the aircraft performance would require reduced MTOW.

Decision between offloading bags and making fuel stop comes down to whether or not the carrier had an option to get the bags to DUB in reasonable time against the cost of a fuel stop (landing, handling, time etc.)

GH

Seat1APlease
4th Sep 2007, 09:22
This is where I'm trying to get a wee bit more technical in the answer.
This is where you open up a can of worms. Firstly it isn't just airfield height temperature and runway lenght which governs the max take off weight, but also runway slope and wind. If there is a stronger headwind then the weight will increase, and vice versa. The prevailing wind will determine which runway is in use and this in turn may have a lower max take off weight because of terrain problems on climb out. If there is high ground off the end of the runway then the aircraft has to be able to clear it on one engine if the other fails on take off. Add these factors together and you can calculate your max weight, but even this won't answer your question for several reasons. Fistly if you are operating a charter aircraft then you probably have 5 seats for every 4 on a scheduled aircraft. If you are full then that may mean an extra 30-40 seats which in round numbers may add four tons to your take off weight. Passsengers, depending on the regulatory authority are also taken to be a standard weight, one for males and one for females, so if it is a rugby charter then a different weight would be used than on a nuns charter to Lourdes. Someone may have a performance manual to hand to give you a max weight for the runway but that may still not answer your question fully. Catania to Dublin is quite a long way as shorthaul flights go, and the reason given does not seem improbable to me. Having said that I am no expert on the performance of the MD83

Shamrogue
4th Sep 2007, 22:30
Guys

Thanks for the answers. Simple straight forward stuff which the public never really gets to take into account.

Well done and thanks again.

Shamrogue