Project Tupolev Team :: View topic - a few questions regarding Ex-1

ha5mvo · ÊÂÑ

Hi,
Before I submit my first tape, I thought I might have a practice run - just to get the feel of it first.
A few things became apparent, primarily, that it all happens too quick Óëûáêà

The exercise calls for a first turn at 200 at which point I should have a clean wing.
With 80T, the vertical speed required to maintain V2+40 (~290-300) up to 120m and then the acceleration through 330 (flaps 15) and 350 (flaps 0) at TO thrust (reduction to nominal only > 260m) gives me about 15 seconds to do all that.
What it means is, that I can't do it in a step-by-step manner (e.g I have to basically retract the flaps almost at one go from 28 to 0)

is it intended to be this way, or did I misunderstand something?

Bell · ÊÂÑ

Hehe.... It is a very good and expected question...

First of all you have to inwardly separate 2 definitions: Flight Manual requirements and Flight Manual recommendations. Where is a difference? For this particular case, V2+40 is recommendation you need to follow for some standard takeoff. But you have to be at 120 m or above and accelerate to 330 km/h or more to start flaps retraction, and that is the requirement. In other words, tha Flight Manual describes general procedures in which aircraft operation is limited by safety factors and engineering limitations but leaves you some room for variation.

If your climb straight or height of crosswind turn is 300, 400 or any other, you can keep V2+40 after rotation before 120 m, after you passed 120 m you can reduce pitch to accelerate up to 330 km/h and start flaps retration as decribed further in Flight manual.

To make the crosswind turn at 200 meters you need to climb this way... After rotation you should set AoA about 9 deg, pitch is about 11-12 deg, and climb to 60 m accelerating to approx V2+40. After you reach 60 m start to reduce pitch with intention to accelerate up to 330-340 km/h at 120-125 m and get vertical speed about 3-4 m/s at this altitude. Not lower than at 120 m and at 330 km/h or above start flaps retraction from 28 to 15 keeping vertical speed at 3-4 m/s. After you accelerated to 350-360 km/h switch the flaps changer to 0 position. Since you are climbing at takeoff thrust and you will have low pitch at this moment, the acceleration goes very quickly, and flaps retraction from 28 to 0 is assumed to be continious. Full wing lift devices retraction if you did all mentioned above properly should be finished at 170-180 m. In the meantime you have to control IAS to avoid its exceed above 400 km/h as requested in the exercise.

At height of 170-180 m and at clean configuration increase pitch and at 200 m start turning. If you start to increase pitch right before or in bank, you'll definitely get G-force of 1,3g-1,4g because of centrifugal force vector influence. That's why in this exercise we rectricted that parameter in the range between 0,8g and 1,2g. You should carry passengers smothly, right? Óëûáêà

So, your goal is to get the clean config at height of 180 m or lower and increase pitch before start the turn at 200 m.

ha5mvo · ÊÂÑ

Thanks for the reply Bell!
I was indeed aiming at 290-300 up to 120m which left me exactly 80m to accelerate to 400, retract the flaps (in two stages - so I thought) stabilize, and then make the turn - obviously, way too much for the very short time those 80 provide Óëûáêà

I'll try to make it as per your recommendation, perhaps run a couple of practice circles before I post the tape - just so it can at least be not too far off the mark Óëûáêà