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Old 4th Jan 2012, 09:49
  #101 (permalink)  
 
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LSM,

I'm afraid your information regarding 175 performance is still incorrect. Given calm conditions on 20 at SOU with a pressure of 1013 the aircraft does not become limited until 28C. Furthermore, RTOM is only restricted by about 150kg at 30C. Obviously, a breath of wind or some high pressure will improve matters. Landing performance is never an issue.

Maybe you didn't use the optimum parameters when doing your calcs. ie T/o 1, ECS OFF, MACTOW >16% ? Or maybe you were using the paper tables?

Given that Flybe limit the MTOM presumably to reduce nav charges, it's not really such a ground-gripper, is it? Obviously, it's also never going to be a long range bucket and spade jet from any airport given the reduced MTOM. Of course, Flybe could choose to increase the MTOM on some of the fleet should they wish to operate some longer routes from longer runways in the future.
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Old 4th Jan 2012, 10:18
  #102 (permalink)  
 
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Given that Flybe limit the MTOM presumably to reduce nav charges, it's not really such a ground-gripper, is it?
Never said it was.

No I don't have access to your nice new iPad but I find it hard to believe that it gives you an extra tonne of performance.

How much does ECS OFF give you?

With a full load of punters how far does 3.5 tonnes get you? Would have been nice if it could get as far as the Dash no?
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Old 4th Jan 2012, 15:04
  #103 (permalink)  
 
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LSM,

“Quote:
Given that Flybe limit the MTOM presumably to reduce nav charges, it's not really such a ground-gripper, is it?

Never said it was.”


I guess I must have misinterpreted your earlier post:

“RJ, trouble is the 175 performance from SOU is sadly lacking, to be kind about it. It's going to struggle to get as far as the Dash with a similar load!”


To do the numbers…..

From your post #88:

“Ignoring the QNH today because I don't know what it was the RTOM at 10C is a gnats cock under 34 tonnes.
Flybe MTOM is 34,999kg. APS is 22,500kg give or take. Max total pax is 88.
88x90 (for cash) = 7920
+ 22,500 = 30,420kg giving you a smudge over 3.5 tonnes of fuel. Enough for Nice? No. That'll probably do you for a Bergerac (maybe) and getting close to an EDI from SOU.
Wait until it gets hotter!”



Let’s just re-work that for RTOM 34,999kg at 28C still air 1013HPa.
34999 – 30420 = 4579 call it 4.5 tonnes for cash.

So, 4.5 Tonnes at 28C, not 3.5T at 10C.

To compare to the D8:

Typical APS 18200 Max pax 78 – x 90kg = 7020 gives a ZFW of 25220kg
Now, at 10C in calm conditions with QNH of 1013 on rwy 20 at SOU the D8 has RTOM of 28727kg, giving a max fuel load of…..3507kg

Bump the temperature up to 28C and you have RTOM of 27850kg, giving a max fuel load of….2630kg

The E175 max fuel load would be 4500kg in either case…..sure, the fuel burn is higher, but not THAT much higher!

Perhaps a better way to look at the 175 would be to say that with an 80% load (70 pax) it can carry about 6000kg of fuel off 20 at SOU in calm conditions on a 30C day.

That takes you a long way into Europe if you put it on a higher yielding route.

The EFB performance app is excellent. It also allows the use of flex in icing conditions. I think the payback time for the ipads will be quite short.
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Old 4th Jan 2012, 19:09
  #104 (permalink)  
 
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“RJ, trouble is the 175 performance from SOU is sadly lacking, to be kind about it. It's going to struggle to get as far as the Dash with a similar load!”

Pretty much what Lord Spandex was getting at.
I think we can all do the sums until we are blue in the face the facts seem to be that the 175 offers nothing over the dash and As Adfly mentioned, a lot of flybe's bases (and importantly the ones they have little or no competition at) have short runways. So the question remains, why have they bought the damb things with those engines?

How much greener is the dash over the 175 on a typical route?
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Old 4th Jan 2012, 20:44
  #105 (permalink)  
 
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RJ,

The quote in your post was a comment made originally to you by LSM!

If you were to read and comprehend "the numbers" in my post you would understand that his understanding of 175 performance was flawed as he doesn't have access to accurate data.

The 175 has no significant performance issues out of SOU. From a practical point of view it out-performs the D8 in terms of range and payload.
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Old 4th Jan 2012, 22:36
  #106 (permalink)  
 
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Sorry Osbo, my understanding is not flawed! Maybe my figures are a bit out of date following the advent of the iPad perf, granted. Still only available to those who have completed the LMS training and I admit it sounds a bit better.

Yes you did misinterpret my post. My point was not one of gettingairborneability rather one of practicality and efficiency when compared to the Dash, which it is replacing.

Even with a Dash load it'll only carry 5.5 tonnes of fuel, same as the Dash and even if you can lift that from SOU you're not getting as far as the Dash full stop. Increasing the RTOM will increase, even further, the operating costs of a 175 as opposed to the Dash.

However, I agree that limiting its passenger load will help. Why not get a 170 in that case...?! AND it's got better runway performance!
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Old 5th Jan 2012, 05:05
  #107 (permalink)  
 
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LSM

“Sorry Osbo, my understanding is not flawed! Maybe my figures are a bit out of date following the advent of the iPad perf, granted. Still only available to those who have completed the LMS training and I admit it sounds a bit better.”

Sorry, your understanding of 175 performance is flawed because it’s based on data that is totally out of date and doesn’t maximise the aircraft’s capabilities using all of the available means. The new performance data is more than “a bit better” – it’s a lot better. For a start, in the example for 20 at SOU we can now make use of the improved performance offered by restricting the MACTOW to more than 16% - that gives an improvement of more than 500kg in itself. From your previous post I gather you didn’t take account of ECS OFF in your calc – that accounts for another 500kg. Also, each T/O calculation benefits from being a precise calculation rather than using worst case data produced to cover a huge range of variables on one sheet of paper.

“Even with a Dash load it'll only carry 5.5 tonnes of fuel, same as the Dash and even if you can lift that from SOU you're not getting as far as the Dash full stop. Increasing the RTOM will increase, even further, the operating costs of a 175 as opposed to the Dash.”

Just a minute! Using your planning data of 90kg/pax, even without performance restriction the max fuel the fully-loaded Dash can carry is:

MTOM 28998kg – TYPICAL ZFM 25220kg = 3778kg!!, considerably less than the 5.5 tonnes you quote!

As demonstrated in the previous post, using the same average pax weights, the 175 can lift a full load of 88 pax with 4500kg of fuel right up to 28C. The Dash starts to suffer from performance reduction when the temperature rises above 5C (15C on rwy 02), so that by the time the temperature reaches 28C it can only carry 2630kg of fuel (3100kg on rwy 02).

Let’s say that those two maximum fuel loads equate to roughly the fuel required (FOB) for the same sector on each aircraft, though the difference in fuel burn will be smaller.

Then to summarise,

1. with a full pax load where neither aircraft is performance limited, they have broadly similar range, but the 175 is carrying 10 more pax.

2. at SOU, where performance is an issue for the Dash, the 175 maintains its payload/range capability whilst the range of the Dash with max payload reduces significantly as the temperature rises. An EFB performance app for the Dash may improve this in the future, but point 1. above will still apply.

3. At airfields with longer runways the Dash and 175 offer similar range but with the 175 able to carry 10 more pax.

4. There is potential to increase the fuel load of the 175 by up to 2500kg (>2hrs flight time) by an increase to MTOM should it be required in future but that would incur higher nav charges for any aircraft so upgraded. This would considerably extend its range capability from longer runways, but it is not relevant to the discussion here.

As for operating costs, suffice to say that Flybe got a VERY good deal on the 175 and we are told that operating costs of the 175 vs Dash are really not a significant issue. Factor in the expected reliability benefits and much-improved customer experience and I think it will prove to be a big success as a Dash replacement on all but the shorter domestic routes.

It certainly does not suffer from performance problems at SOU, which is where all of this began with the incorrect statement that “trouble is the 175 performance from SOU is sadly lacking, to be kind about it. It's going to struggle to get as far as the Dash with a similar load!”

It's simply not so!

Last edited by osbo; 5th Jan 2012 at 07:24.
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Old 5th Jan 2012, 11:00
  #108 (permalink)  
 
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Hang on osbo, if we are clutching at straws which is what we would be to gain the performance we require the Dash example if not correct.

Taking the Flap 10 Bleeds off Alternate 20 emerg turn @10c wind calm 1013, the RTOM is 29241 . . . . in excess of our company MTOW of 28998.

So therefore on could carry 4021kg of fuel in your theoretically aircraft APS weight.

To make this a balanced argument I thought I should point this one out. Sadly this chart much like your ipad thingy is not always readily available but is published on AIMS!!

Rgds,
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Old 5th Jan 2012, 11:27
  #109 (permalink)  
 
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CaptAirProx

I don't understand the "clutching at straws" reference. I can't find the chart to which you refer on he Intranet, The 20alt chart gives the numbers I have used. But given that it is correct it would make little difference as it's only giving a couple of hundred kilos and the performance will already be dropping off given the 29241 figure.

I really can't be bothered with arguing the toss over this any further. All I wanted to do was correct the false impression of the 175 given by some of the posts on his thread. Anyone who cares to read and digest the numbers will see that it is a credible replacement for the Dash even at SOU.

Happy New Year!

Last edited by osbo; 5th Jan 2012 at 12:58.
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Old 5th Jan 2012, 13:34
  #110 (permalink)  
 
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Osbo,

1. As someone who, until last year, taught aircraft performance I can assure you that my understanding of aircraft performance is not flawed. As I admitted, I am using older figures than the iPad performance.

2. In the interest of a balanced argument why don't you compare the two types using the same performance? Old paper stuff or iPad stuff. Or will you continue to ignore the fact that the Dash performance is going to improve and restore the balance!? I am, of course, assuming that the improvement for the Dash will be largely in line with the 175. A point not provable either way.

3. In which case all of the figures are accurate. IE at 10C the Dash will lift 4.0 tonnes (according to Capt AP) and the 175 4.5 tonnes according to you.

Who's going further?

For the sake of argument and only as a demonstration:

Dash at LRC will use about 800kg/h. TAS of 300kts.
175 at LRC will use about 1400kg/h (generous). TAS of 420kts (generous).

Giving the Dash an extra 150nm at least. Less fuel and less nav charges! So, reliability aside (I agree with you on that point) which is the more economical?

Even if you limit the 175 to 78 pax and carry 5.5 tonnes of fuel and using more sensible FF and TAS of 1500kg/h and 400kts the range is about the same. Still using more fuel and higher nav charges though!

I'm happy for you to show me the figures for the iPad performance for both types because until then your point is moot.
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Old 5th Jan 2012, 14:53
  #111 (permalink)  
 
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Apologies Osbo. Guys, I think you can all do as many calculations as you like the fact of the matter is your working very hard to find small details especially you Osbo. I'm sure your figures are very accurate but surely you can agree that when spending half a billion on new equipment the advantages should be as clear as day! Even after all your hard work thats far from the truth so the question remains why? The only answer I seem to arrive at is snobbery.

Plus all this rubbish about reliability, the fact is these props are used pretty rigorously on all sorts of routes, often on short sectors and after a few years they are going to need a bit of tlc. Sure the 175's will to although I don't think they are going to be such a success.
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Old 5th Jan 2012, 22:23
  #112 (permalink)  
 
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Osbo - don't worry the 'clutching at straws' reference was not intended to be personal.

If you go onto the Q400 Perf section, ignore the destination charts and go for the link ALL OTHER AIRFIELDS you will find all the non optimum charts for many airfields we operate. It has proved handy to keep a copy of these charts in the back pocket (another metaphor?) so the Dash can get it up - so to speak.

Btw my sole intention with my post was to correct the false impression of the Dash, in that it is overtly limited. It appears not at SOU using the figures I have available to me.
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Old 6th Jan 2012, 05:58
  #113 (permalink)  
 
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Good to hear

Good to hear that the 175 is not performance limited out of SOU because as our most successful base it would have been foolish to buy an aircraft that you couldn't use from there.

In terms of why the 175 is better it's a far superior aircraft to travel on - quieter, smoother, less vibration, more room, better seats, faster. Frankly it staggers me that so many people are prepared to entertain the Dash - especially on the longer routes out of SOU (say anything over 1.5 hrs - and that's a lot of routes). Every time I fly as a pax I'm astounded how noisy it is in the cabin with all that resonance from the overhead bins etc.

And that's before you touch on the thorny subject of reliability...

DP
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Old 6th Jan 2012, 08:12
  #114 (permalink)  
 
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CAP

Thanks for the pointer – strange that such a useful chart isn’t more easily accessible. It gives 02-like perf on 20.

LSM

I don’t for one second doubt your credentials as a performance guru and I’m sure your flight planning is up there with the best too. My reference to your lack of knowledge was solely with regard to 175 performance as used in Flybe today. I intended no offence. I didn’t come here looking for a fight with anyone and I’ve certainly got nothing against the Dash, which has done great things for the company.

I only came out of PPRUNE hibernation to correct the false notion that the 175 is a dog in terms of performance out of SOU. You (unintentionally) gave inaccurate figures in your posts that painted a very poor picture of what the jet could do. You wrongly said that in summer things would be even worse.

Implied in your last post is that you now accept that while the 175 may not be able to travel quite as far out of SOU as the Dash in the winter it will go rather further in the summertime, which is when it matters. Yes, that may change to some degree with the introduction of an EFB in the future, but that’s really not the point – we are talking about the situation today. Reference to operating costs etc are just muddying the waters and a separate topic.

I'll leave it there and slip back into hibernation, I’m sure you’ll want the last word.

Cheers,
O
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Old 6th Jan 2012, 08:48
  #115 (permalink)  
 
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Osbo, not a case of having the last word, merely defending ones argument just like you have done in your previous post. This debate does seem to have run its course though, going on your well worked figures I guess we will see in the summer if any new routes open as a result of the 175's addition. If not then the question remains why invest half a billion, why not just get more dash's like porter etc.
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Old 12th Jan 2012, 13:17
  #116 (permalink)  
 
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SOU-NWI

News release from Flybe today regarding a new Summer Saturday service to NWI. Firmly aimed at the cruise pax market by the looks:

Flybe | Corporate | Media | News archives

I think this will be operated by the Dornier being based in NWI to do the MAN and EXT flights during the week. So, a former Suckling Dornier may be returning to SOU?
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Old 12th Jan 2012, 13:37
  #117 (permalink)  
 
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Vueling

After deinyng the flights from Southampton they are now online from 23rd June

Flights to Southampton

Regards
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Old 12th Jan 2012, 15:31
  #118 (permalink)  
 
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A quick search reveals NWI will be flown by a Q400. Also, fantastic to hear about Vueling finally adding BCN!!

So, as it stands...

New Routes S12:

Flybe:

NWI - 1 weekly Q400 (Sat) Summer Seasonal

Thomas Cook:

IBZ - 1 weekly BE E195 (Sat) Summer Seasonal

Vueling:

BCN - 3 weekly A320 (Tue, Thu, Sat) Unknown if Summer only or year round as yet.
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Old 12th Jan 2012, 17:50
  #119 (permalink)  
 
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Adfly:
Not one to doubt your sources but the press release for the NWI route states Loganair plus the timings suggest it will operate NWI-SOU-NWI. As I believe there will only be a Scotairways Do328 aircraft based there for the summer I find it unlikely that it will be a Dash 8. The route is surely a filler at best. Happy to be proved wrong but I can't see the demand for 78 seats with the additional expense of a couple of positioning sectors to be fair!
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Old 12th Jan 2012, 17:50
  #120 (permalink)  
 
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NWI-SOU

The new route will be operated by the Dornier, not a Q400. I think you have gone just by the ecolable but carry on to the seat assignment and you will see the seatmap.
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