Tristar descent attitude

[flipflopman RB199]

Evening all,

Without wishing to start with an apology, I'm sorry if this is a stupid question..

Whilst having discussion about emergency descents in differing aircraft, a colleague who was formerly on 216, stated that the T* aircraft could not dive!

His reasoning being that as Lockheed developed the TriStar, passenger comfort was paramount and consequently, was designed to maintain a constant 5 degrees nose up.

Now, my first reaction, having never been involved with TriStars is to think that I am the victim of a massive Waah, however, knowing a little about their fancy ACS systems and the like, I can also imagine a glimmer of truth hiding in there somewhere...

Can anyone shine a light and solve a bet?


Flipflopman

[14greens]

Right and wrong, the TriStar can dive, and may have a slight nose down attitude in an emergency descent, its nothing major though.
Would you call it a dive? probably not, ROD in an emergency can exceed 6000fpm even so
However, in a standard descent you were given correct info, she keeps a positive nose up attitude otherwise they may spill the g&T and they did not want that! Cruise attirtude is about 5 deg nose up
Bit like most "modern" airliners today the DLC system means the final approach is conducted with a fairly stable nose up attitude all the way to the threashold. ROD is controlled by spoiler deployment rather than pitch through the DLC system. ACS is something a bit different.

[Old Fella]

Your friend is getting confused. He is obviously thinking about the DLC (Direct Lift Control) which causes the spoilers to deploy to about a 7 degree NULL setting when Landing Flap is extended. The effect is for the spoilers to move toward the stowed position in response to back-stick movement or to deploy further in response to forward-stick movements. The result is a stable body angle on approach by increasing of decreasing lift by the spoiler action. In the event of an emergency descent being required at altitude the DLC system is not in use as the flaps would be in the retracted position, however the spoliers could still be deployed manually.

[LFFC]

His reasoning being that as Lockheed developed the TriStar, passenger comfort was paramount and consequently, was designed to maintain a constant 5 degrees nose up.

It didn't really have anything to do with passenger comfort. Most wide body aircraft can produce a lot of lift from the fuselage, so are generally designed to fly in the cruise with a few degrees of nose-up attitude to make use of it. I believe that when Lockheed shortened the TriStar fuselage to produce the long-range -500 version, they lost more lift than expected so had to extend the wings to compensate; hence the need for the Active Control System (ACS) to relieve the load on the wings. Of course, shortening the fuselage between the wings and the tail also reduced rudder effectiveness - but that's another story.

As for "TriStar could not dive"; it's just like any other aircraft.

[Dengue_Dude]

The cruise attitude was more about body lift - just look underneath if you doubt it.

We often had 6,000 fpm rate of descent when on 216 tankers when practising Emerg Descent, but this was a limit at the time to do with venting the extra fuselage tanks.

I don't know if the lim was removed later - also, isn't 6000 fpm the end of the range shown on the RCDI? Can't honestly remember.

The technique required for the most effective Emergency Descent was idle power, boards out and using about 30 degrees of bank (in 1993 anyway) and airspeed on the bug (i.e. short of VNE), it went down very quickly, but not with much of a nose down attitude at all. Obviously it rather depends on WHY you're having to go down in the first place.

I presume that's what he meant when he said it couldn't dive - which is patent dross.

[flipflopman RB199]

Thanks fellas,

Some very good explanations there. Exactly as I'd imagined, the truth often lies square in the middle! Always worth asking the people in the know however!

Question answered...

Out of curiosity now then, as I'd imagined, the TriStar is just like any other jet as goes diving, has anyone had first hand experience of this, and did it require much manual input?


Flipflopman

[NutLoose]

It can even land without flaring. :E indeed without any input whatsoever from the crew.. It can also leap tall buildings in a single bound... Well at least 80ft tall ones from the said landing:E

[Dengue_Dude]

Those main spars aren't all they're cracked up to be, especially after 'leaping' 80 feet or so.

I put my whole arm in THAT one, in the port main wheel bay . . .

Perhaps that's what happens when you stuff the nose down (despite it saying don't do it in ACM).

Nostalgia eh?

[MAINJAFAD]

Humm, I think that one had something to do with 'Aircraft landed Heavily in Autoland' as stated in a number of Joke F700 entries kicking around the internet.

Though the fault recification was in this case 'ILS used does not support Autoland'.:ugh::ugh::ugh: