Weather during cruise
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Weather during cruise
I would appreciate it if you would share your techniques or methods for weather avoidance/penetration during cruise (e.g. penetrating a front, etc.). I personally like to fly 2000 ft or so below optimum and avoid laterally as much as practical. On that respect I have heard people going to HDG SEL and limiting bank angle to 15. Furthermore, if your optimum altitude and max altitude are the same, are the applicable margins those for max altitude or for optimum altitude. Thanks in advance for your feedback.
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Don, what aircraft are you flying? The specific answers will vary depending on aircraft type. 2000 ft below optimum sounds quite conservative to me, but the relationship between optimum and maximum altitude will depend on aircraft type and even carrier. If you're actively avoiding weather there's a good chance you're going to be in HDG mode anyway
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Talking about a relationship to OPT ALT while discussing turbulence is meaningless unless you mention the a/c type.
What a/c impacts the spread between OPT vs. MAX ALT. 737NG w/winglets is approx. a 1700' spread. 777 is approx. 3800' spread between OPT/MAX altitude. So OPT ALT in a 737NG w/winglets is 1700' below MAX. To get 1700' below MAX ALT in a 777 would put you 2100' above OPT ALT.
For Boeing's the larger the a/c the better it's buffet margin performance is while at OPT ALT. Most a/c can maintain OPT ALT at 1.3G turbulence but some have to descend. At 1.5G turbulence at OPT ALT most have to descend but some can climb.
I'm not sure if this is related to the buffet margin differences mentioned above but at OPT ALT the 'window' between the max and min speed tapes on the 777 is about 50% greater than on a 737.
X number of feet below OPT ALT? IMO not a factor.
Bank angle reduction? IMO that's a good technique for all high altitude ops.
What a/c impacts the spread between OPT vs. MAX ALT. 737NG w/winglets is approx. a 1700' spread. 777 is approx. 3800' spread between OPT/MAX altitude. So OPT ALT in a 737NG w/winglets is 1700' below MAX. To get 1700' below MAX ALT in a 777 would put you 2100' above OPT ALT.
For Boeing's the larger the a/c the better it's buffet margin performance is while at OPT ALT. Most a/c can maintain OPT ALT at 1.3G turbulence but some have to descend. At 1.5G turbulence at OPT ALT most have to descend but some can climb.
I'm not sure if this is related to the buffet margin differences mentioned above but at OPT ALT the 'window' between the max and min speed tapes on the 777 is about 50% greater than on a 737.
X number of feet below OPT ALT? IMO not a factor.
Bank angle reduction? IMO that's a good technique for all high altitude ops.
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For the 737NG, I've heard this if your interested...
To decide whether you can maneuver over or around...
Work out:
Range x 100
x tilt (in degrees) (-1.5 deg)
= height in feet above your level!
Has anyone actually used this to gauge cloud buildups?
To decide whether you can maneuver over or around...
Work out:
Range x 100
x tilt (in degrees) (-1.5 deg)
= height in feet above your level!
Has anyone actually used this to gauge cloud buildups?
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My shout:
Cruise level change should be based on MAX not OPTIMUM - OPT depends on CI and I am NOT interested in company 'savings' in Mod-Severe turbulence.
EW - use of scanner angle is (should be?) standard practice taught to all F/Os and based on the 1 in 60 rule. Do NOT forget the radar beam is NOT a pencil beam, though, and is several degrees deep, so the 'tops' may not be where you think they are.
Yes to no LNAV, HDG SEL please (we ARE talking Mod-Severe, yes?)
Maintain max available margin between low speed and high speed buffet limits.
Cruise level change should be based on MAX not OPTIMUM - OPT depends on CI and I am NOT interested in company 'savings' in Mod-Severe turbulence.
EW - use of scanner angle is (should be?) standard practice taught to all F/Os and based on the 1 in 60 rule. Do NOT forget the radar beam is NOT a pencil beam, though, and is several degrees deep, so the 'tops' may not be where you think they are.
Yes to no LNAV, HDG SEL please (we ARE talking Mod-Severe, yes?)
Maintain max available margin between low speed and high speed buffet limits.
. . and DON'T FORGET you're in Hdg Sel.
Start clock, put time marker on pink string, mark radio log, ask for coffee - just do something so you don't go soldiering on at the next turn
No, I haven't, but probably more by luck than innate skill.
Start clock, put time marker on pink string, mark radio log, ask for coffee - just do something so you don't go soldiering on at the next turn
No, I haven't, but probably more by luck than innate skill.
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To decide whether you can maneuver over or around...
Work out:
Range x 100
x tilt (in degrees) (-1.5 deg)
= height in feet above your level!
Has anyone actually used this to gauge cloud buildups?
Work out:
Range x 100
x tilt (in degrees) (-1.5 deg)
= height in feet above your level!
Has anyone actually used this to gauge cloud buildups?
Personally, I wouldn't trust the radar to determine the tops above FL200 or so... There might be a buildup ahead of you giving a very weak, or no return at all if you point the antenna ahead.
My take on it is to use lower tilt angles to scan the lower parts of clouds and treat any radar echo as if it were at my altitude, unless I can positively determine visually that the tops are significantly below...
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Thanks for all the answers. Yes, I was referring to the NG 700 and 800, 24 and 26 K, respectively. About using HDG SEL, as many say, that would be the usual mode for constant deviations. I was not sure though about the need to limit bank angle to 15. I wanted to check general practice. I was also not sure about OPT vs MAX alt as my FCTM states 0.5 margin for OPT vs 0.3 for MAX and sometimes both are the same. Thanks again.
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CI impact on OPT ALT? Often zero and rarely more than a couple hundred feet. And on Boeing's if OPT ALT has a significant change due to CI it typically impacts MAX ALT. The exact amount depends upon the CI entered, a/c type, and the weight of the a/c.
Restricting yourself to 2000' or 4000' below OPT ALT will typically force you down into the low to mid 30's. In tropical areas I'm typically scratching for all the altitude I can(at least OPT ALT and possibly higher depending upon a/c type) and restricting myself to X thousands of feet below OPT ALT is the exact opposite strategy I'd use.
Eg. OPT ALT 370. The techniques mentioned would restrict you to FL 330 or FL 350. I'd chose FL370, perhaps FL380, and depending upon a/c type perhaps FL390. The difference between FL330 and FL370/380 or 390 can be significant.
Restricting yourself to 2000' or 4000' below OPT ALT will typically force you down into the low to mid 30's. In tropical areas I'm typically scratching for all the altitude I can(at least OPT ALT and possibly higher depending upon a/c type) and restricting myself to X thousands of feet below OPT ALT is the exact opposite strategy I'd use.
Eg. OPT ALT 370. The techniques mentioned would restrict you to FL 330 or FL 350. I'd chose FL370, perhaps FL380, and depending upon a/c type perhaps FL390. The difference between FL330 and FL370/380 or 390 can be significant.
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No one chooses to fly in moderate or svr turbulence. So it's often a situation that you just have to deal with the best you can.
Is OPT ALT acceptable for the overwhelming majority of the flying we experience? Based on my experience the answer is yes.
Do I restrict cruise to fly around 2000-4000' below OPT ALT for typical weather? No. Thunderstorms? No.
Are cruise levels restriced for turbulence? All the time. Happened on both of my last two trips. In radar contact it's easy enough to get Pireps or be the weather ship yourself if no one else has checked it out.
Last trip we checked with ATC and we could out climb it. Reported FL280-360. Instead of flying 11,000' below OPT ALT(FL260) we flew 1000' above OPT ALT(FL380) in smooth air. Would we have stayed there in moderate turbulence? No, we'd have flown at FL260 in smooth air.
Non-radar? You have to be a lot more cautious. Pireps of mod-svr turbulence along our flight path while non-radar (overwater). Dispatch figured we could be 1000' above the turbulence if we were willing to fly 1000' below MAX ALT. Four pilots, 60,000+ hrs experience, and none of us thought that was a good plan while non-radar. Dispatch with zero heavy jet experience was surprised that we choose to fly across the pond in the upper 20's _I'll have to upload another 10,000 lbs of fuel." Four pilots looking at speaker (SATCOM) thinking the same thing - yeah, so what!?!? Sometimes caution is warranted.
Two to four thousand below OPT ALT as a technique? IMO overkill.
Is OPT ALT acceptable for the overwhelming majority of the flying we experience? Based on my experience the answer is yes.
Do I restrict cruise to fly around 2000-4000' below OPT ALT for typical weather? No. Thunderstorms? No.
Are cruise levels restriced for turbulence? All the time. Happened on both of my last two trips. In radar contact it's easy enough to get Pireps or be the weather ship yourself if no one else has checked it out.
Last trip we checked with ATC and we could out climb it. Reported FL280-360. Instead of flying 11,000' below OPT ALT(FL260) we flew 1000' above OPT ALT(FL380) in smooth air. Would we have stayed there in moderate turbulence? No, we'd have flown at FL260 in smooth air.
Non-radar? You have to be a lot more cautious. Pireps of mod-svr turbulence along our flight path while non-radar (overwater). Dispatch figured we could be 1000' above the turbulence if we were willing to fly 1000' below MAX ALT. Four pilots, 60,000+ hrs experience, and none of us thought that was a good plan while non-radar. Dispatch with zero heavy jet experience was surprised that we choose to fly across the pond in the upper 20's _I'll have to upload another 10,000 lbs of fuel." Four pilots looking at speaker (SATCOM) thinking the same thing - yeah, so what!?!? Sometimes caution is warranted.
Two to four thousand below OPT ALT as a technique? IMO overkill.
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I fly 737 - 800.
My FCTM says to limit bank angle to 10 degrees if near MAX altitude ( possible
pitch limit indicator appearing or stick shaker if turning at 25 degrees bank
and encountering moderate to severe turb. )
It's also much more comfortable for the pax.
My FCTM says to limit bank angle to 10 degrees if near MAX altitude ( possible
pitch limit indicator appearing or stick shaker if turning at 25 degrees bank
and encountering moderate to severe turb. )
It's also much more comfortable for the pax.
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Two to four thousand below OPT ALT as a technique? IMO overkill.
As far as bank angle, it's been a few years since I last flew Boeing, but in my opinion selecting a reduced bank angle at the same time as HDG mode is selected is probably not a bad habit to get into. I try to couple actions so they're automatic (KISS for dumb-arses such as me) when things get busy. If you're up near max you'll need the reduced bank angle anyway, if down lower you can always increase the bank angle if something pops up at the last minute, or (especially during the day) you can see you won't make the turn before running into something behind the buildup.
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Another technique to use when operating near altitude limits is to go to the N1 page and manually select CON as the max power available. Normally CRZ power will be selected automatically and will make about 97% N1 available. Selecting CON will make around 100% available. (It resets the N1 bugs)
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This modern desire to have 'golden rules' on how to do x, y or z is wrong. Each flight requires attention to the particular problems it generates. The simple rule is to maintain adequate manoeuvre margin. How you do it, by speed, bank angle, or cruise altitude is entirely up to you and the 'event'. No one should EVER view this as 'restricting' you' to anything.
To newer pilots, however, BEWARE the idea of simply 'climbing above' the weather. It often looks attractive but can kill and has done. Often it is, of course, an option, but particularly in tropical areas weather can rapidly outclimb you and significant turbulence can often extend several thousand feet above the cloud tops in clear air in an unstable air mass.
To newer pilots, however, BEWARE the idea of simply 'climbing above' the weather. It often looks attractive but can kill and has done. Often it is, of course, an option, but particularly in tropical areas weather can rapidly outclimb you and significant turbulence can often extend several thousand feet above the cloud tops in clear air in an unstable air mass.
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In Gloomy weather I generally do...
-Tilt around - 2/Map Range 40 or 80 NM
-avoid laterally using HDG mode
-have a margin of of at least 300 Ft to max FMGC Alt. when it is bumpy
A/C is A320
Worked well so far
Safe Flying
CptRegionalJet
-Tilt around - 2/Map Range 40 or 80 NM
-avoid laterally using HDG mode
-have a margin of of at least 300 Ft to max FMGC Alt. when it is bumpy
A/C is A320
Worked well so far
Safe Flying
CptRegionalJet
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Beware having in mind a 'fixed' idea of radar tilt/range. In significant weather you MUST keep the scanner moving up and down to see the whole picture, and keep checking at different ranges.
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BOAC...Tranks for your concern....
Of course flying around with fixed settings is not a Good technique.
Like you mentioned every new WX scenario needs a different approach just like every Range change needs a tilt adjustment.
Values I mentioned are just my General Approach when confronted with adverse weather,just what Don Gato asked for.
Safe Flying
CptRegionalJet
Of course flying around with fixed settings is not a Good technique.
Like you mentioned every new WX scenario needs a different approach just like every Range change needs a tilt adjustment.
Values I mentioned are just my General Approach when confronted with adverse weather,just what Don Gato asked for.
Safe Flying
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Cpt RJ- I use -1 @ 80 miles and -2 @ 40 miles. 40 miles is the big decision point. And in tight situations the range cycles through 80, 40, 20, and 10 miles.
Nothing like having the cockpit lights as dim as possible trying to see if the horizon or stars are blocked by a cloud.
And the joy of timing turns, often on the 10 or 20 mile scale, and watching a buildup slide past your wing in the dark or a break in the overcast. MAX gain is your friend at altitude. 
Nothing like having the cockpit lights as dim as possible trying to see if the horizon or stars are blocked by a cloud.
And the joy of timing turns, often on the 10 or 20 mile scale, and watching a buildup slide past your wing in the dark or a break in the overcast. MAX gain is your friend at altitude.
Last edited by misd-agin; 9th Oct 2012 at 13:05. Reason: spelling
