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WalterLeo · ÊÂÑ

The flight manual gives two pages:
3.2 Take off weight (28 deg flaps) and 3.4T.O. distance.

Following table 3.2 a T.O. from Mexico City (2300 m altitude) and 86 to for a flight of 1600 km to Habana would not be possible with a 30 deg C temperature, wihich is quite normal in summer there. Only if you select flaps 15 (see tables 3.3 and 3.6) you could take off. The Rwy 05 L 23 R of MMMX has nearly 5 km of length. Why the weight restriction, having plenty of runway?

Best greetings

Walter

Bell · ÊÂÑ

Hi, Walter,

TOW in the table 3.2 is restricted by climb gradient. If the runaway length allows you to perform take-off with the flaps at 15*, you should do this way. Otherwise, leave some passengers and luggage in the Mexico City... or pour off the fuel. Óëûáêà

WalterLeo · ÊÂÑ

Thanks for your answer, now I understand: Its the climb gradient after T.O. which brings in that restriction. In the case of the Tu-154 the difference is considerable!

Thanks

Walter

Quax · Ïðàâàê

Inspired by Walters topic I started playing with the Tushka at La Paz, Bolivia, SLLP (Elevation AMSL 13,325 ft / 4,061.5 m), what is equal with begging for problems, all the more with ISA+36 (the all-time-high I found for La Paz). Õèòðûé

But therefore I performed a ferry flight with just one checkup man and 4to ballast in the forward holds for the CG...

Better than expected I got the APU and the engines running and the A/C airborne. But soon with the lift off sirena got in rage. Although I´ve prepared the cabin in accordance with the manual this procedure brought the cabin altitude not within the limits ´cause it´s stopping with airport altitude minus 200m on ground. While climbing the pressure diff grow but the cabin altitude stood constant, even levelling off at save-to-ground altitude didn´t help. I had pretty good 6 units flow in both main ducts (even with idle on ground, what I can´t understand for the moment...)

Any better ideas than switching off the sirena? Lowering the value at the pressure setup window was also no solution to the problem (as it would just rise the diff pressure to the limits).
By the way, the russian procedure with setting the altimeter to QFE has its limits above 3000m - the pressure scale isn´t wide spread enough Íåò

- although it´s, compared with QNH not nearly as bad.

Best regards and thanks in anticipation!

Quax · Ïðàâàê

I hope, it doesn´t work, it would be another clear case of "RTFM"! Õèòðûé

So I just found this in the manual, some additional infos about problems with pressurisation. It seems, this fits to the incident described above:

"For cabin pressure loss:

1) double check the alarm to confirm a rise in cab. altitude
2) check for availability of air bleed
3)turn off the siren switch
4)turn off the PSVP switches
5) open the flow valve completely (the list indicates a value of 7-8 units)
6) turn on the backup ARD switch (behind the green cap)
7) monitor the cab. altitude"

I´ll try it out tomorrow, it´s almost midnight...

Best regards from EDDR!

WalterLeo · ÊÂÑ

Cubana was operating with the 154M flights in and out Óëûáêà

of La Paz, see that:
http://www.protu-154.net/forum/viewtopic.php?p=172500#172500
What can happen with PT 154 M (and it happened to me in MMMX) that in the flight preparation the cabinaltitude did not reach 650 mm HG and therefore the automatic controller did not "kick in". When that happend to me my "FI" fiddeld around with the manual valves putting more air into the cabin and it worked, automatic controller took over. The passengers wrote angry letters to my airline complainig sudden earpopping!
Óäèâëåíèå

Regards

Walter

Bell · ÊÂÑ

If the absolute pressure at the airport level is lower than 650 mm Hg you should set this absolute pressure on the pressure setup window but not 650 as recommended in the English Flight Manual. Did you do that?

WalterLeo · ÊÂÑ

Presumably not! But how can I get the absolute pressure altitude? After consulting some old books out of my days of real flying and using GOOGLE I think one could say:
In terms of standart atmoshere the absolute pressure altitude of MMMX 2230 m should be around 22,22 (8000 ft) in HG or 566 mm HG (formulas here:
http://www.wrh.noaa.gov/slc/projects/wxcalc/formulas/pressureConversion.pdf
Would be this value to be put into the pressure controller or must be corrected this value with the actual temperature? 8000 ft at 30 deg celsius would be 11500 ft or 19,5 in/HG or 25.4*19,5=495 mm HG

Thanks Bell!

Regards

Walter

Bell · ÊÂÑ

Just enter QFE. For calcutaing over QNH to QFE you divide airport elevation (in meters) into 11 meters and deduct this number from QNH value.

If at MMMX, for example, QNH=1000 hPa=750 mm Hg and elevation is 2230 meters than QFE will be equal to 547 mm Hg. (750-2230/11).

Quax · Ïðàâàê

Hi WalterLeo, Hi Bell!

Unfortunately the procedure for pressure loss as described in the manual didn't work (it was headlined with "what you do in the real A/C", so may be this is not implemented in the PT-Tu) as it didn't help to set the QFE at the pressure setup window with Bell's formula (yesterday i did make a rough estimate of 450 Torr, with the formula it's 390.5 for SLLP). To be quite honest: things got some worse with the correct value (about 500-600m higher cabin altitude). Also "fiddeling around" at last with the valves was no key to success. 3600m cabin altitude, about 400m lower than SLLP (all the same!) was the reachable limit.

What a pity, but La Paz is a really extrem place to try things like this.

Walter, you mentioned Cubana flying with the -154 to La Paz. Regrettably Cubana had to pay a high toll for operating hot and high with a fatal crash on 29th August 1998 at Quito-Mariscal Sucre International (SEQU / Ecuador, Elevation AMSL 9,228 ft / 2,813 m). They had hard trouble to get the 154M-engines running, aborted the T/O two times while the third abortion led to the crash.
And, interesting for you as fan of Tushka and Mexico, they also lost a Tu-154B-2 in Mexico City-Juaréz after overrunning the runway - but I bet you know. Õèòðûé

Well, thanks a lot for your help! All the best to you!

Bell · ÊÂÑ

Hi Guys,

are you sure that Cubana was operating at La Paz on Tu-154M? Or it was Walter's joke? Óëûáêà

There is operating restriction for Tu-154M take-off and landings at the airports with elevation below -305 meters and above 2500 meters MSL.

The operation range for Tu-154B2 is from -300 up to 3000 meters.

If La Paz has elevation at 4 061,5 meters, you can't operate there on Tu.

WalterLeo · ÊÂÑ

1) Operation La Paz: at least Osmani who is working with CUBANA had said in
http://www.protu-154.net/forum/viewtopic.php?p=172500#172500
they were operating there. Dont know if he is not mixing it up with Quito.
A pity that some months ago Osmani changed his flat and is silcenced since then.

2) That Cubana overshot at MMMX and wrecked a Tu-154b2 I didnt know, but thanks for the information.
Strange that this accident is not included in the accident databases like:
http://www.airdisaster.com/cgi-bin/view_details.cgi?date=02091967&reg=CU-T827&airline=Cubana+de+Aviacion
(Was it on T.O. or landing? Victims?)
There was a Cubana Crash near MMMX but with an AN 12 1967 cause: inflight bomb explosion.
But besides that MMMX is not an easy place to fly, high altitude, high mountains around, crowded airspace, at the end of RWY 23 L/R a massive steelfence in place of a gentle overrun, not so easy approaches to RWY 05 L/R and in summer high tempratures.

3) Thanks Bell for the nice formula and your explanations!

4) By all our admiration for the Tu-s: Seems the engines (at least for the 134 and the b2) were powerful but not allways so reliable as they should be. But in the simulation its not a problem!
Óëûáêà

Bell · ÊÂÑ

WalterLeo · ÊÂÑ

Maybe at Cubana they were doeing things, Mr. Tupolev should never hear about? "Flying on a wing and a prayer" like the US pilots say if they wander outside the approaved envelops.

Regards

Walter

Óëûáêà

Quax · Ïðàâàê

Hello the two of you!

It's an satisfying explanation by Bell, thanks for that!

The accident at Mexico City-Juaréz International happend on 14th September 1991 with CU-T1227 (c/n 82A541). They landed long and the overrun suffered extensive, irreparable damage so that the Tu-154B-2 was lost. It's not reported if members of the crew or passengers suffered any harm.

Thanks again for all your responses!
Best regards!