DC-8 two-engine ferry?
Joined: Oct 2004
Posts: 1,199
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From: Hunched over a keyboard
oops - finger trouble! I meant to say that V1 must be HIGHER than Vmcg.
My understanding of V1 is, for the record:
V1 is a decision speed at at which you have the option to stop or go in the event of a failure of the critical power unit.
It is slow enough for you to be able to stop in the remainder of the ASDA but high enough for you to be able to continue in the remainder of the TORA and TODA. It is also ABOVE Vmcg in order that you are able to maintain directional control up to Vr.
There is a two second "reaction" time built in to the calculations so that if you spot a failure at V1 there is sufficient time for your brain to process the information and your hands and feet to take the appropriate action to reject the takeoff.
However, this is not the same as allowing an extra two seconds of decision making time - the two seconds is for reaction to a decision made at V1.
Ferrydude: I was not commenting upon the DC8 per se (read my posts and you'll see that is the case). I was responding to a comment by another contributor who claimed that no aeroplane would have a better range with an engine shut down.
This is not the case, for example with the C130 as mentioned by another contributor, and with the B737, Jetstream and others. Now, I know that the B737 and Jetstream are twins, but I'm sure that the last time I looked a Herc had 4 motors!
My understanding of V1 is, for the record:
V1 is a decision speed at at which you have the option to stop or go in the event of a failure of the critical power unit.
It is slow enough for you to be able to stop in the remainder of the ASDA but high enough for you to be able to continue in the remainder of the TORA and TODA. It is also ABOVE Vmcg in order that you are able to maintain directional control up to Vr.
There is a two second "reaction" time built in to the calculations so that if you spot a failure at V1 there is sufficient time for your brain to process the information and your hands and feet to take the appropriate action to reject the takeoff.
However, this is not the same as allowing an extra two seconds of decision making time - the two seconds is for reaction to a decision made at V1.
Ferrydude: I was not commenting upon the DC8 per se (read my posts and you'll see that is the case). I was responding to a comment by another contributor who claimed that no aeroplane would have a better range with an engine shut down.
This is not the case, for example with the C130 as mentioned by another contributor, and with the B737, Jetstream and others. Now, I know that the B737 and Jetstream are twins, but I'm sure that the last time I looked a Herc had 4 motors!
Last edited by moggiee; 8th April 2005 at 13:07.
Joined: Jun 2003
Posts: 497
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From: Near LOACH intersection
Fair enough Moggiee, I'll re phrase my post. I say there is no way in hell that the Diesel 8 is more efficient in long range cruise with one or more engines secured. Anyone out there pontificating about such efficiencies, please prove me wrong. Meanwhile, I suppose I'll go an dig through the cellar for the old manuals.
Joined: Apr 2004
Posts: 258
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From: vancouver oldebloke
Moggiee,nearly right V1 as defined with FAA part25-107 stipulates that the failure(VEF) has to be 'recognized' and 'reacted to'BY V!.....
the 2 seconds part is in the 25-109?"TAke off Distance"...In that a 2 seconds worth of distance ,at V1 speed,is included in the T/Off distance...FAA/JAR 25-109(a)(2)
JAR reads the sameway(JAR 25-107(a)(1)
the 2 seconds part is in the 25-109?"TAke off Distance"...In that a 2 seconds worth of distance ,at V1 speed,is included in the T/Off distance...FAA/JAR 25-109(a)(2)
JAR reads the sameway(JAR 25-107(a)(1)
Guest
Posts: n/a
3 engine T/O
Maurizio,
Yes, that is how I remember it too. The only other point that emerges from the past is that the max BRW was severely reduced, quite a surprising amount. But it's all such a long time ago.....
And tonight it's a reunion with an ex-air force colleague, so I shall definitely take up your your brilliant suggestion. Maar dit sal 'n dop of twee of meer seker wees.
ou Drek Toppie
Yes, that is how I remember it too. The only other point that emerges from the past is that the max BRW was severely reduced, quite a surprising amount. But it's all such a long time ago.....
And tonight it's a reunion with an ex-air force colleague, so I shall definitely take up your your brilliant suggestion. Maar dit sal 'n dop of twee of meer seker wees.
ou Drek Toppie
Joined: Dec 2004
Posts: 11
Likes: 0
From: Switzerland
On DC-10 and MD-11 there are official procedures for 2-eng. ferry
flights in case of technical problems to reposition the aircraft.
No passengers allowed and many procedures/restrictions to be
followed. The company I worked with was rather generous applying 2-eng. ferry on the MD-11 until they had a fire warning
on one of the life engines on such an occasion. It was a false warning but after that event things were handeled more re-
strictive.
I don't think you'll be able to save fuel on a passenger jet by
shutting down engine(s) in cruise-you'll be slower and will have
to fly lower-just check respective tables for all eng. cruise against
eng. inop. cruise. Not to mention possible legal requirements.
And some engines don't like beeing windmilled for
hours (lubrication problems).
Cheers, jojodel
flights in case of technical problems to reposition the aircraft.
No passengers allowed and many procedures/restrictions to be
followed. The company I worked with was rather generous applying 2-eng. ferry on the MD-11 until they had a fire warning
on one of the life engines on such an occasion. It was a false warning but after that event things were handeled more re-
strictive.
I don't think you'll be able to save fuel on a passenger jet by
shutting down engine(s) in cruise-you'll be slower and will have
to fly lower-just check respective tables for all eng. cruise against
eng. inop. cruise. Not to mention possible legal requirements.
And some engines don't like beeing windmilled for
hours (lubrication problems).
Cheers, jojodel
Joined: Feb 2001
Posts: 441
Likes: 5
From: Midlands,UK
While in the states on a Metro III course I heared about drug runners using Metro's to ship from South America into the states and extending there range by shuting down one and cruising on the other. This results in a 50% reduction in fuel flow and about a 25% loss of speed. When you do not have to conform to regulations there are some great savings out there.
Joined: Feb 2004
Posts: 75
Likes: 0
From: Perth
Trying to get a Mixmaster off on one is an excercise in patience! Like about 11,000' of it with just the rear, more if it is front only! I'll pass on that unless it is at Edwards thanks.
That said, shutting down the front and flying on rear only increased both range and endurance significantly. Was done as a SOP by the spotters for Chennes Beach Whalers long ago.
Anyone who cycles the gear with only one turning is in for a Green, Round, type of time!!
That said, shutting down the front and flying on rear only increased both range and endurance significantly. Was done as a SOP by the spotters for Chennes Beach Whalers long ago.
Anyone who cycles the gear with only one turning is in for a Green, Round, type of time!!
Joined: May 2003
Posts: 412
Likes: 0
"While in the states on a Metro III course I heared about drug runners using Metro's to ship from South America into the states and extending there range by shuting down one and cruising on the other. This results in a 50% reduction in fuel flow and about a 25% loss of speed. "
Wow. If you can get that much more range by shutting down just one engine, imagine the possibilities with a DC8 shutting down 3!!
Hawk
Wow. If you can get that much more range by shutting down just one engine, imagine the possibilities with a DC8 shutting down 3!!
Hawk
Nexialist
Joined: Jul 2003
Posts: 182
Likes: 2
From: Milton Keynes
From reading about the antics of drug smugglers, they seem to like flying at low level, which would mean that 2 engines would be operating at low power (inefficient), so shutting down one and perating the remaining at high power (more effiecient) would seem doable for increased range. Also the smugglers have , I would imagine, a somewhat cavalier regard for rules, getting caught for flying on one, would pale into insignificance compared to a ton of coke in the back.
Joined: Apr 2005
Posts: 26
Likes: 0
From: USA
DC8 Ferry flight on 2 eng
I am a DC8 check airman and during my training at UAL the 2 eng ferry flight was never mention. In the AFM doesn't even consider the 2 eng Ferry flight, all the performance charts are made for the 3 eng ferry flight. Besides all that, I don't think that the DC8 at any given weight with any kind of engines could fly in the event of a 3rd eng failure.
At a weight of 300.000lbs the airplane needs way too much power to start the taxing on 2 engines.
At a weight of 300.000lbs the airplane needs way too much power to start the taxing on 2 engines.
