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Tri Jets  
User currently offlineKaddyuk From Wallis and Futuna, joined Nov 2001, 4126 posts, RR: 26
Posted (12 years 3 months 2 weeks 3 days 15 hours ago) and read 1166 times:

Does anyone know if it is possible for a Tri Jet (MD11, DC-10, L1011) to run on the engine in the tail, or will it plummet to the ground if it was tried?




Whoever said "laughter is the best medicine" never had Gonorrhea
12 replies: All unread, jump to last
 
User currently offlineThirtyEcho From United States of America, joined Dec 2001, 1643 posts, RR: 1
Reply 1, posted (12 years 3 months 2 weeks 3 days 14 hours ago) and read 1113 times:

Yo, Kaddyuk, you've been watching too many 1930s-era airplane movies. No airplane plummets to the ground with the engines off unless Errol Flynn is flying it. How much thrust do you think the engines are putting out as an aiplane makes a normal descent?


User currently offlineKaddyuk From Wallis and Futuna, joined Nov 2001, 4126 posts, RR: 26
Reply 2, posted (12 years 3 months 2 weeks 3 days 14 hours ago) and read 1095 times:

I know it wont "plummet" straight away, but if you turn both engines off on a 777 it will crash eventually


Whoever said "laughter is the best medicine" never had Gonorrhea
User currently offlineEssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 2
Reply 3, posted (12 years 3 months 2 weeks 3 days 13 hours ago) and read 1078 times:

Sure it's possbile, but under what conditions? Defining them is crucial...

Let's see...the books says a 727-200Adv, jt8d-7, Std OAT, 1 pack, no anti ice, clean, max cont epr. I'll give 2 points of a straight line curve, max alt (y axis) vs gross weight (x axis):

12000 ft at 110000 lbs to 2000 ft at 145000lbs

for a -15 powered a/c, same parameters

16000 ft at 110000 lbs to 2000 ft at 162500

Interpolate to find intermediate values...
So, yes, it's possible to fly on 1 engine.

Cheers


User currently offlineAA737-823 From United States of America, joined Mar 2000, 5722 posts, RR: 11
Reply 4, posted (12 years 3 months 2 weeks 3 days 8 hours ago) and read 1040 times:

What the hell just happened here?

I saw it coming... I saw it here... I saw it fly by STRAIGHT OVER MY HEAD and though, "geez, what was that?"

Interpolate this.

 Smile


User currently offlineEssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 2
Reply 5, posted (12 years 3 months 2 weeks 3 days 7 hours ago) and read 1034 times:

OK - I'm bored tonight.

It's a linear relationship...

1. draw the x axis going from 0 to 200000 lbs, marked every 5000 lbs
2. draw the y axis going from 0 to, say, 20000 ft in 1000 ft increments.
3. the result is a graph w/ 40 units in the x axis, and 20 units in the y axis.
4. plot (for the jt8d-7) the points (110000, 12000) and (145000, 2000).
5. we're talking about a linear relationship, so determine the slope (delta y/delta x, which = 10000/-35000)
6. so the slope = -.2857. (common sense check, negative slope means the alt capability decreases as the weight increases, so that's good)
7. use the point slope formula. (y-y1)=m (x-x1)
8. (y-12000) = -.2857(x-110000)
9. solve for y
10. y= -.2857x + 43427
11. plug in x=145000 to check the math, should be 2000.
12. 2000.5. close enough (rounding errors)
13. So for any weight b/t 110,000 lbs (about as light as a functional 727-200adv can be) and 200,000 lbs, plug it in for x, and the equation in item 10 above spits out the altitude a -7 powered a/c can maintain w/ the prescribed limitations.
14. remember algebra????????


cheers-


User currently offlineRizzes From United States of America, joined Dec 2000, 5 posts, RR: 0
Reply 6, posted (12 years 3 months 2 weeks 3 days 7 hours ago) and read 1033 times:

While not a tri jet, there was a A330 that landed in the Azores last year without any power. According to a "Dateline" report last week, all fuel had leaked out of the aircraft and flew without power for 20-25 minutes to land successfully with minor injuries.

A quiet ride from 35,000 feet to sea level without power.


User currently offlineChdmcmanus From United States of America, joined Mar 2001, 374 posts, RR: 2
Reply 7, posted (12 years 3 months 2 weeks 2 days 20 hours ago) and read 994 times:

This is a post from about 2 weeks ago…

http://www.airliners.net/discussions/tech_ops/read.main/35763/

As for the -10, yes. You have to get your GW down to around 380 or below. Above that the acft will not level off. For Single engine ops you perform a driftdown and either land or set up a cruise-climb Spec Range profile to make the closest airplane patch and land. If the Acft is light on cargo/pax, its no problem, just dump gas to performance mins and go. If you have cargo/pax (high ZFW) it gets tricky (The pax seem to object to being jettisoned). The acft handles acceptably in a clean config, and can handle around 22/ext on the Flaps/Slats, but once you get the gear down you are committed to landing. The apu is available to assist with Pneu/AC and elec but depending on why the 2 engines failed the hydraulics may get a little sluggish.

Regards,
ChD



"Never trust a clean Crew Chief"
User currently offlineKaddyuk From Wallis and Futuna, joined Nov 2001, 4126 posts, RR: 26
Reply 8, posted (12 years 3 months 2 weeks 2 days 20 hours ago) and read 983 times:

I wasnt really talkin about a glide slope to stay in the air,
A B747 Can FLY (ie:Not a lifethreatening emergency) run with 2 engines. Can a Tri Jet SAFELY maintain altitude and continue to fly SAFELY?




Whoever said "laughter is the best medicine" never had Gonorrhea
User currently offlineEssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 2
Reply 9, posted (12 years 3 months 2 weeks 2 days 20 hours ago) and read 977 times:

What do you mean by "Safely"? Getting to the first available airport and landing uneventfully?

A trijet was designed to fly on 3 engines. If 2 engines are taken out of the equation, the a/c has been hugely impacted from a performance standpoint, which cuts redundancy and impacts safety greatly, but the overall anwser is, a trijet can fly on 1 engine depending upon the specific details such as weight, density alt, etc.....Got it???


User currently offlineChdmcmanus From United States of America, joined Mar 2001, 374 posts, RR: 2
Reply 10, posted (12 years 3 months 2 weeks 2 days 20 hours ago) and read 978 times:

What EssentialPowr and myself have been saying; it depends upon weight. If the GW is low enough, yes, the acft will naturally settle into its altitude based on thrust (aka "Driftdown"). If the weight is above the thrust capabilities, the acft will simply descend until alt is 0 (that's bad). Effectively, you only have one method of reducing weight in an emergency, dispensing fuel. If the route of flight is over land with plenty of options, you dump to your weight capabilities and land at the first available cement strip. If you are over water or an area with no available airfields, you compute the amount of fuel required to a destination, add that to the ZFW, and dump to this limit (aka performance limit). If this weight is still above the thrust/altitude capabilities, you will be forced to ditch or emergency land. In this case you dump to the thrust/alt limit and fly it as close to civilization as possible, then perform a planned ditch/emerg landing.

Regards,
ChD



"Never trust a clean Crew Chief"
User currently offlineKaddyuk From Wallis and Futuna, joined Nov 2001, 4126 posts, RR: 26
Reply 11, posted (12 years 3 months 2 weeks 2 days 13 hours ago) and read 936 times:

OK, Thanx
All comments have been most helpful



Whoever said "laughter is the best medicine" never had Gonorrhea
User currently offlineBen From Switzerland, joined Aug 1999, 1391 posts, RR: 50
Reply 12, posted (12 years 3 months 2 weeks 1 day 23 hours ago) and read 904 times:

Part of the design specifications for the Tupolev Tu-154 was the requirement to be able to take-off with only 2 engines operational, and be able to fly straight and level (indefinitely) with only 1 engine working.... but that is an aircraft with a high thrust to weight ratio anyway.

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