The great big "ask an airline pilot" thread!

Sparkrite

Hi,
Here's one I have pondered about........

Say you are traversing the Atlantic, west to east, at say, FL350 at Mach 0.90 with a tail wind (jet stream) of approx. 200Knts, if only says you :-).

Now all of a sudden the tail wind drops dramatically and suddenly to say half that ie. 100Knts. will momentum cause the aircraft to momentarily go above mach1 ?

Is this possible, does it happen or does the jet stream never alter by that much, so quickly, for this to be a concern ?

Thanks in advance.

Growler!!!

This has been explained a couple of time before. There are a number of speeds to consider.

The airspeed will remain the same but the ground speed will change with loss of tail wind. The aircraft doesn't " know" it has a headwind or tailwind.

Sparkrite

Growler!!! wrote: »

This has been explained a couple of time before. There are a number of speeds to consider.

The airspeed will remain the same but the ground speed will change with loss of tail wind. The aircraft doesn't " know" it has a headwind or tailwind.

Sorry, I couldn't find it anywhere.

I understand about the difference between A/S and G/S, however if there is a sudden drop in tailwind then surely due to momentum there will be an increase in air speed, albeit only momentarily. It is this short lived increase I am inquiring about should the craft already be close to Mach 1.

Growler!!!

With a drop in tailwind the ground speed will decrease regardless of any other force acting. The airspeed will remain the same. It is indicated airspeed only we are interest in. The indicated airspeed will not exceed Mach 1.

Sparkrite

Growler!!! wrote: »

With a drop in tailwind the ground speed will decrease regardless of any other force acting. The airspeed will remain the same. It is indicated airspeed only we are interest in. The indicated airspeed will not exceed Mach 1.

Thanks for your quick replies.
Maybe I am not explaining this properly, or there again maybe I am ranting. :-)

Ok, you are happily cruising along at an IAS of Mach0.9 and suddenly your tailwind drops by 100Knts. surely this is akin to an apparent increase, while momentum allows, of that 100Knts differential as a headwind.

If this drop in tailwind is sustained then your G/S will obviously drop by 100Knts as well so it stands to reason that the craft will have less momentum. This change/loss in momentum has to have expended energy somewhere, ie. in the sudden "apparent" increase of headwind.

Please be aware that I know that the craft will/can not sustain this short lived apparent increase in A/S but my question was if cruising close to mach 1 can it cause problems?

Maybe in "real life" these sudden changes do not occur but surely it must be catered for, just in case......

If I remember correctly, when I was current as a PP, and was taking off with a tail wind component any drop in that tail wind had a positive effect on my A/S. I know this is not quite the same, but hopefully you can get what I am trying (probably very badly) to ask.

bkehoe

What Growler is saying is true if its a gradual decrease in tailwind but if its a rapid change then what you say is indeed possible.

This is because the aircraft has momentum, the groundspeed essentially. Because of this momentum (a heavy aircraft does not loose momentum quickly), if there is a rapid change in head or tailwind component then of course the indicated airspeed will increase or decrease. Its most common to see this on approach in gusty wind conditions at low altitude where sudden changes in the wind speed are more likely. Or on approaches in places like Tenerife where a significant tailwind initially in the approach changing to a significant headwind at lower altitudes is common. Most pilots who've flown to TFS can vouch for that (and most have probably had go arounds due to this!).

I have personally had Mmo exceedance (nowhere near Mach 1 though as my type cruises below 0.80 normally) due to a rapidly decreasing tailwind which dropped from approx 120kts to 40kts in the space of about 10 miles. Also associated with quite a bit of turbulence.

Sparkrite

bkehoe wrote: »

What Growler is saying is true if its a gradual decrease in tailwind but if its a rapid change then what you say is indeed possible.

This is because the aircraft has momentum, the groundspeed essentially. Because of this momentum (a heavy aircraft does not loose momentum quickly), if there is a rapid change in head or tailwind component then of course the indicated airspeed will increase or decrease. Its most common to see this on approach in gusty wind conditions at low altitude where sudden changes in the wind speed are more likely. Or on approaches in places like Tenerife where a significant tailwind initially in the approach changing to a significant headwind at lower altitudes is common. Most pilots who've flown to TFS can vouch for that (and most have probably had go arounds due to this!).

I have personally had Mmo exceedance (nowhere near Mach 1 though as my type cruises below 0.80 normally) due to a rapidly decreasing tailwind which dropped from approx 120kts to 40kts in the space of about 10 miles. Also associated with quite a bit of turbulence.

Thank you, EXACTLY what I was wondering. So it stands to reason if cruising close to Mach 1 then a rapid drop in tail wind could cause a short venture into super sonic.
Is this catered for in modern airliners?

bkehoe

The Mne speed is when any single part of the airflow around the aircraft goes supersonic (and this will happen before the aircraft itself reaches Mach 1) and there would be a buffer between this and Mmo; therefore flying below Mmo is essential. We have a procedure for preventing overspeeds or recovering from an overspeed but its nothing special. Mmo on most types I know is well below 0.90.

I'm not sure of any commercial types that would cruise close to even Mach 0.9. The 777 only cruises at 0.84 at high cost indexes for example, and aircraft like the 737 and A320 are quite happy around 0.77/0.78.
It would take a huge increase in airspeed to bring the speed close to Mach 1.

Of interest, didn't the Air China 747 that went into a spiral dive after an incorrectly handled engine failure in the cruise off the coast of the US briefly exceed Mach 1 in its descent?

Sparkrite

I remember that Air China incident, must look it up, can't remember what speeds it hit in its precarious decent.

A quick Google for the B747 gives me varying Mno speeds ranging from 0.85 - 0.92, with the latter being its Mne.

At FL350 a sudden drop in tailwind of 100Kts (don't know if this happens at all) would bring it frighteningly, or at least some surfaces of the ship, close to Mach1.

It was about 2 months back that I flew from KJFK to EIDW with a flight time of 5:02. We enjoyed a G/S at times in excess of 760MPH and it was then I started pondering my initial question. Crazy or what?

Anyway thanks for the answers lads/lassies.

VG31

I was on an EI A320 recently and noticed some unusual noises that I have never heard before. Could someone please explain them?

The first was when the aircraft was taxiing to the gate there was a high pitched noise in the cabin that lasted for a few minutes. I can't really describe this noise any better.

The second was once the aircraft had arrived at the gate there was a noise that sounded like someone sawing through wood. It obviously couldn't be that but that's what it sounded like. This noise lasted around 30 seconds, max 1 min.

Thanks!

IITYWYBMAD

VG31 wrote: »

I was on an EI A320 recently and noticed some unusual noises that I have never heard before. Could someone please explain them?

The first was when the aircraft was taxiing to the gate there was a high pitched noise in the cabin that lasted for a few minutes. I can't really describe this noise any better.

The second was once the aircraft had arrived at the gate there was a noise that sounded like someone sawing through wood. It obviously couldn't be that but that's what it sounded like. This noise lasted around 30 seconds, max 1 min.

Thanks!

I'd imagine that that's the PTU (power transfer unit) you're hearing. Google PTU and Airbus and you'll see what it does and why.

eatmyshorts

https://disciplesofflight.com/pilot-shortage-where-did-pilots-go/

An interesting read on how the bean counters are destroying the industry.

Tenger

eatmyshorts wrote: »

https://disciplesofflight.com/pilot-shortage-where-did-pilots-go/

An interesting read on how the bean counters are destroying the industry.

I read that myself. I agree with the majority of it.
Definitely a wholly US centric point of view. Aviation culture is different in the EU (and possibly in Asia/Pacific)

Less pilots today than in 1980 may be partially explained by 2 man cockpits and higher average flying hours.

But I wholeheartedly agree with the increasing level of cynicism among aviation staff. No longer are you seen as an asset to the airline, now you are a YoY rising cost that needs to be curtailed or removed from the organisation. "accountancy led mgmt" is a nice phrase.

smurfjed

COPORATE CAPTAIN REQUIRED

For private aircraft operated from Munster, Ireland.
Minimum requirements for this role
• 1500 Hours total pilot time
• 500 Hours Multi Engine Jet as PIC
• FAA- CPL (ATPL an advantage)
• Current FAA Medical – Class 2 Minimum
• Type rating (Embraer Phenom 300) an advantage but not essential
Please forward CV to Secretary by clicking on the 'Apply' button

Is the Phenom that easy to fly? I would have thought that the insurance requirements would require more experience than this.

Growler!!!

smurfjed wrote: »

Is the Phenom that easy to fly? I would have thought that the insurance requirements would require more experience than this.

Saw that advertised in the national press. From what I remember of the private jet industry in Ireland, if a position is not filled through word of mouth and the old school tie network then the terms and conditions aren't great!

I hear the owners other jet on frequency very often so the crew are busy.

smurfjed

FlexFoil™ variable geometry control surfaces represent a major improvement over conventional aircraft flaps. By exploiting the natural elasticity of aviation grade materials the FlexFoil™ control surface changes the camber of a wing during flight by shape morphing rather than through the heavy and cumbersome mechanisms of conventional wing assemblies. Shape morphing performs the large controlled deformations (from -9° to + 40°) needed for landing and takeoff without separating from the rest of the wing. Our new approach also permits discrete span-wise twist of the compliant edge at high response rates (30 degrees/sec.) to reduce induced drag and withstand external loads (air loads, inertial loads etc.), yet it is strong and stiff with very small and distributed strains on the mechanical structures and control surfaces.

What an amazing concept, with drag reductions between 5-12% for long range aircraft, I wonder how long it will take for corporate aircraft manufacturers to introduce them?

_Tombstone_

smurfjed wrote: »

What an amazing concept, with drag reductions between 5-12% for long range aircraft, I wonder how long it will take for corporate aircraft manufacturers to introduce them?

Airplane Coatings Help Recoup Fuel Efficiency Lost To Bug Splatter

When bugs explode against the wings of oncoming airplanes, they create a sticky problem for aerospace engineers.

“A bug doesn’t know that it’s been catastrophically destroyed,” says Emilie J. (Mia) Siochi, a materials scientist with the National Aeronautics & Space Administration. “Its blood starts to thicken as if it’s healing any other injury.”
This bug blood, or hemolymph, clings to an airplane’s wings, disrupting the smooth airflow over them and sapping the aircraft’s fuel efficiency.

The team explored different combinations of polymer chemistry and surface structure and reports that it has created a coating that could reduce the amount of insect insides stuck to the wings by up to 40%.

With further optimization, such coatings could allow planes to use 5% less fuel

https://www.youtube.com/watch?v=6o1D4fi8mTk

Lots of upgrades for them to do.

smurfjed

This bug blood, or hemolymph, clings to an airplane’s wings, disrupting the smooth airflow over them and sapping the aircraft’s fuel efficiency.

Can we call this parasite drag

Tenger

smurfjed wrote: »

......



What an amazing concept, with drag reductions between 5-12% for long range aircraft, I wonder how long it will take for corporate aircraft manufacturers to introduce them?

I think they have been reading some dale Brown, he had skin morphing tech on his revamped EB-1's and EB-52's in most of his novels.

I had to read them for 'research' reasons........:rolleyes:

amen

I wonder how long before bullets are coated in this reducing the capacity of a persons blood to clot...

fricatus

amen wrote: »

I wonder how long before bullets are coated in this reducing the capacity of a persons blood to clot...

Yeah, don't you just know there's some bugger out there, lacking in all conscience and thinking up the design!

Tenger

amen wrote: »

I wonder how long before bullets are coated in this reducing the capacity of a persons blood to clot...

Am sure its been looked at. However that would end up with more dead enemy that wounded. When fighting a peer on peer modern war you want to make the enemy waste logistics and resources on non-frontline operations.
Thus more wounded inflicted puts strain on their logistics train and overall force moral. This is a better outcome that just killing the opponent troops.

eatmyshorts

Thread direction??

Tenger

Tenger wrote: »

..............

Good point eatmyshorts....this isn't the Squawk as you CFIT thread.
Shame on the quoted poster!!

smurfjed

http://www.dailymail.co.uk/travel/travel_news/article-3160775/From-Paul-Newman-s-whisky-demands-tending-needs-celebrity-dog-life-private-jet-pilot-revealed.html

How the other half operate :)

pepe the prawn

A question for any pilots who use cork, how come it's rare to see/hear any commercial traffic using the standard arrival procedures such as in Dublin? I'd have thought that for example a Tismo1R or Kurum 1R would be the likely one for traffic particularly coming from the Glasgow/Edinburgh and Manchester/Birmingham routes... It's always radar vectors to establish on the ILS or sometimes I hear the the traffic being asked if they would like to self position...

Is it just because cork isn't that busy so getting the traffic lined up and on the ground isn't a priority such as it is in Dublin? . Always made me curious... Thanks :-)

Growler!!!

Up to a number of months ago ATC would radar vector all arrivals to 2500ft to either ROVAL or GOSDA ( approx 7nm from the runway) depending on the runway in use. That way the aircraft were established on the Localiser and below the Glideslope.

Now, ATC can only send aircraft to BARNU or ATLAM (12nm from runway). However ATC will offer radar vectors for a shorter approach.

All the above goes out the window when it gets busy ( for ORK). Everyone is left on the full STAR to provide spacing. Runway 35 isn't too bad as the aircraft roll to the taxi ways but on runway 17 ATC have to allow for the backtrack.

pepe the prawn

Growler!!! wrote: »

Up to a number of months ago ATC would radar vector all arrivals to 2500ft to either ROVAL or GOSDA ( approx 7nm from the runway) depending on the runway in use. That way the aircraft were established on the Localiser and below the Glideslope.

Now, ATC can only send aircraft to BARNU or ATLAM (12nm from runway). However ATC will offer radar vectors for a shorter approach.

All the above goes out the window when it gets busy ( for ORK). Everyone is left on the full STAR to provide spacing. Runway 35 isn't too bad as the aircraft roll to the taxi ways but on runway 17 ATC have to allow for the backtrack.

So when they are cleared to BARNU or ATLAM is it a case of programming that waypoint into the FMS and let the autopilot do its thing then?

So must all traffic now be positioned on finals at 12 miles? Or can they be radar vectored to a point less than 12 miles to establish on the localiser?

Growler!!!

pepe the prawn wrote: »

So when they are cleared to BARNU or ATLAM is it a case of programming that waypoint into the FMS and let the autopilot do its thing then?

So must all traffic now be positioned on finals at 12 miles? Or can they be radar vectored to a point less than 12 miles to establish on the localiser?

In the FMS when the runway in use is selected and then the STAR, all of the waypoints are automatically selected. The autopilot will do its thing and route to each in turn.

An example would be for instance if on the TISMO 1R arrival to 17 routing to TISMO ATC may ask do we want to self position (to BARNU @12nm) or take radar vectors for a shorter approach (radar directed to ROVAL @7nm). It's easier for us to self position as we can use the RNAV function to turn at BARNU and route to just before the Final Approach Point which is ROVAL in this case. This may differ in other airlines.

pepe the prawn

Growler!!! wrote: »

In the FMS when the runway in use is selected and then the STAR, all of the waypoints are automatically selected. The autopilot will do its thing and route to each in turn.

An example would be for instance if on the TISMO 1R arrival to 17 routing to TISMO ATC may ask do we want to self position (to BARNU @12nm) or take radar vectors for a shorter approach (radar directed to ROVAL @7nm). It's easier for us to self position as we can use the RNAV function to turn at BARNU and route to just before the Final Approach Point which is ROVAL in this case. This may differ in other airlines.

Great, thanks for the answer, it always bugged me what was the backstory behind it