Firewall an NG - what do you get
IDG,
Yes you can put in a fixed de-rate, on our 26k aeroplanes you can use derate -1 which is 24k and derate -2 which is 22k.
The Vol 1 says that rated thrust is achieved at a thrust lever position less than the forward stop - ie there are more n1's available if you poke the lever forward.
V1MCG isn't a huge issue, even at 26k it is only around 108-110 knots.
you would have to be pretty light to be using speeds that low.
Yes you can put in a fixed de-rate, on our 26k aeroplanes you can use derate -1 which is 24k and derate -2 which is 22k.
The Vol 1 says that rated thrust is achieved at a thrust lever position less than the forward stop - ie there are more n1's available if you poke the lever forward.
V1MCG isn't a huge issue, even at 26k it is only around 108-110 knots.
you would have to be pretty light to be using speeds that low.
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DHD
One of the benefits of using a fixed de-rate is being able to lift a greater weight off very short runways when you are 'relatively' light.
In a -500 TriStar for example we could lift up to 20T more off short runways because we were derating to a 22B thrust instead of the full 524 power. This amounted to some 8000lbs less per engine. Admittedly the short fuselage -500 was quite Vmcg limited, but even so I am surprised that full power is available when using a fixed de-rate.
This is not the case on the 'bus'.
One of the benefits of using a fixed de-rate is being able to lift a greater weight off very short runways when you are 'relatively' light.
In a -500 TriStar for example we could lift up to 20T more off short runways because we were derating to a 22B thrust instead of the full 524 power. This amounted to some 8000lbs less per engine. Admittedly the short fuselage -500 was quite Vmcg limited, but even so I am surprised that full power is available when using a fixed de-rate.
This is not the case on the 'bus'.
Moderator
.. a few comments
(a) lomapaseo was pushing a sensible risk management line - the electronics in modern aircraft may not save the day every time (recent history indicates, quite clearly, that they don't - what's that you say ? our PCs have bugs as well in the software ?) but they can prevent the ham-fisted pilot from creating more problems than he/she might solve by being innovative. It is a question of maximising the probability of a satisfactory outcome .. no guarantees only consideration of risk minimisation and probabilities ....
(b) one poster suggested that he/she would prefer to clip the tree tops, overboost and climb away .. that's fine ... but the risk is that you might also overboost, lose it, and impact wingtip first .. which scenario do you prefer ? .. a controlled impact or blazing saddles cartwheeling ? I guess one might prefer the "die with his boots on" attitude .. but the problem is far more complex than one of the simple "I'll save us ... " philosophy.
(c) I note that Flight Detent was somewhat impolite in his/her response to lomapaseo. Please, good folk, can we keep posts in this forum focussed on the topic and leave the colour to other, more appropriate, forum threads. Here we play the ball ... not the man.
(d) if you predicate a takeoff on a derate configuration (as contrasted to reduced thrust) and then push up the levers, especially at low weights and speed schedules, you expose yourself to Vmcg/Vmca problems. If you haven't been there (and are not familiar with the VERY rapid onset of divergence with many aircraft) and are not trained to react appropriately rather than in panic ... I suggest that you consider not pushing the levers up other than VERY, VERY cautiously. Do keep in mind that it is not just a case of being near the published Vmcg/Vmca but that an increase in thrust may result in a considerable INCREASE in the realworld Vmcg/Vmca. It is a little disturbing to read what appears to be a gung-ho approach to this consideration in many of the posts in this thread ?
(e) Overrun's post makes for interesting reading ...
(f) the main concern, I suggest, is one of turbine temperature (and gearbox loads in the case of turboprops). Modern turbine blades are thermally critically loaded and, in cases of growth engines, don't necessarily have much fat for the pilot to play with ... you over temp such animals at your peril .. and the consequences may not be very long in following the overtemp incident. I am aware of one recent investigation where, with such an engine, an apparently innocuous overtemp did considerable crystalline damage to the blades ... and cost the operator a fistful of money to rectify.
(g) dehavillandriver ... please don't cite the source of confidential documents .. XYZ management might not appreciate your quoting from company confidential documents in a public forum without authority to do so .. if you must so quote, then please leave out the citation ...
(a) lomapaseo was pushing a sensible risk management line - the electronics in modern aircraft may not save the day every time (recent history indicates, quite clearly, that they don't - what's that you say ? our PCs have bugs as well in the software ?) but they can prevent the ham-fisted pilot from creating more problems than he/she might solve by being innovative. It is a question of maximising the probability of a satisfactory outcome .. no guarantees only consideration of risk minimisation and probabilities ....
(b) one poster suggested that he/she would prefer to clip the tree tops, overboost and climb away .. that's fine ... but the risk is that you might also overboost, lose it, and impact wingtip first .. which scenario do you prefer ? .. a controlled impact or blazing saddles cartwheeling ? I guess one might prefer the "die with his boots on" attitude .. but the problem is far more complex than one of the simple "I'll save us ... " philosophy.
(c) I note that Flight Detent was somewhat impolite in his/her response to lomapaseo. Please, good folk, can we keep posts in this forum focussed on the topic and leave the colour to other, more appropriate, forum threads. Here we play the ball ... not the man.
(d) if you predicate a takeoff on a derate configuration (as contrasted to reduced thrust) and then push up the levers, especially at low weights and speed schedules, you expose yourself to Vmcg/Vmca problems. If you haven't been there (and are not familiar with the VERY rapid onset of divergence with many aircraft) and are not trained to react appropriately rather than in panic ... I suggest that you consider not pushing the levers up other than VERY, VERY cautiously. Do keep in mind that it is not just a case of being near the published Vmcg/Vmca but that an increase in thrust may result in a considerable INCREASE in the realworld Vmcg/Vmca. It is a little disturbing to read what appears to be a gung-ho approach to this consideration in many of the posts in this thread ?
(e) Overrun's post makes for interesting reading ...
(f) the main concern, I suggest, is one of turbine temperature (and gearbox loads in the case of turboprops). Modern turbine blades are thermally critically loaded and, in cases of growth engines, don't necessarily have much fat for the pilot to play with ... you over temp such animals at your peril .. and the consequences may not be very long in following the overtemp incident. I am aware of one recent investigation where, with such an engine, an apparently innocuous overtemp did considerable crystalline damage to the blades ... and cost the operator a fistful of money to rectify.
(g) dehavillandriver ... please don't cite the source of confidential documents .. XYZ management might not appreciate your quoting from company confidential documents in a public forum without authority to do so .. if you must so quote, then please leave out the citation ...
John Tullarmarine.
The regos and thrust ratings are public domain - just go and check the CASA and or ASA (avcharges) website if you are so concerned.
The quote from the manual is not company specific, so I accept your point, however I see no reason to cite the company name - company names are attached to posts alleging all manner of thing, most of them unflattering, with no editing.
The use of a company name assists in putting the information into context.
The regos and thrust ratings are public domain - just go and check the CASA and or ASA (avcharges) website if you are so concerned.
The quote from the manual is not company specific, so I accept your point, however I see no reason to cite the company name - company names are attached to posts alleging all manner of thing, most of them unflattering, with no editing.
The use of a company name assists in putting the information into context.
Moderator
Good friend, DHD,
Sorry to be pedantic .. but no company identification, please, (whether direct or indirect) where such identification may
(a) bring the site or this forum into disrepute
(b) lead to the occurrence of calls in relation to the items from legal people to Danny et al on the top floor. I note that such occurrences are likely to be accompanied by follow-on calls from Danny et al to the moderators of this forum and, now that we chaps are getting older .. we really need our sleep).
Forum policy as in the sticky.
Not negotiable in this forum - period.
regards,
JT
(modified for clarification after sleeping on it for the night - without phone calls from Danny)
Sorry to be pedantic .. but no company identification, please, (whether direct or indirect) where such identification may
(a) bring the site or this forum into disrepute
(b) lead to the occurrence of calls in relation to the items from legal people to Danny et al on the top floor. I note that such occurrences are likely to be accompanied by follow-on calls from Danny et al to the moderators of this forum and, now that we chaps are getting older .. we really need our sleep).
Forum policy as in the sticky.
Not negotiable in this forum - period.
regards,
JT
(modified for clarification after sleeping on it for the night - without phone calls from Danny)
Last edited by john_tullamarine; 23rd Mar 2004 at 21:20.
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- 700 22K firewall you get 24 K + something
- 800 24k firewall you get 26K + something
- 900 26K firewall you get 26 K + something
the something is what keeps the engine from exceeding EGT limits
- 800 24k firewall you get 26K + something
- 900 26K firewall you get 26 K + something
the something is what keeps the engine from exceeding EGT limits
