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Quad engines and reverse thrust use

Posted: Wed Apr 17, 2019 5:41 pm
by LAXffDUB
Just did some plane spotting at LAX. I watched an A380 touch down and was surprised to see reverse thrusters only being deployed on engines #2 and #3. Every quad I've ever flown on used all engines for reverse thrust. My question is can the flight crew manually select which engines to use and if so, what conditions would allow/require it? Or does the aircraft's systems automatically make that decision based on pre-programmed parameters? Thanks!

Re: Quad engines and reverse thrust use

Posted: Wed Apr 17, 2019 5:47 pm
by ALTF4
I'm not an A380 pilot, so I am open to being corrected here. However, my understanding is that the pilots can command reverse on whichever engines they desire. On Boeing aircraft, for example, that would involve only engaging the reverse levers for the engines they wish to use.

Additionally, maintenance could "lock out" the thrust reverse actuators on the engines, preventing them from being used even when commanded. Unsure if this is an issue if commanded but "locked out"; e.g. does it actually still attempt to engage reverse or if the FADEC sees that and blocks it.

Finally, some aircraft don't have reverse thrust on all engines... and, in fact, this is the case on the A380 - so what you saw happen is entirely normal. ;-)

Re: Quad engines and reverse thrust use

Posted: Wed Apr 17, 2019 5:55 pm
by stratclub
The A380 does not have T/Rs on engine 1 and 4. And yes, T/Rs could be deployed independently.

Re: Quad engines and reverse thrust use

Posted: Wed Apr 17, 2019 7:27 pm
by thepinkmachine
The reason for A380 having thrust reversers only on inboard engines is that the outboards are far out and might be hanging over the grass, this increasing the risk of FOD.

Re: Quad engines and reverse thrust use

Posted: Wed Apr 17, 2019 7:34 pm
by Farsight
I believe the A380 doesn't have reversers installed on the 1 & 4 engines due to those engines being so far from centreline, putting them at risk of foreign object damage.

Re: Quad engines and reverse thrust use

Posted: Wed Apr 17, 2019 8:51 pm
by stratclub
Airbus didn't want T/Rs at all, but the regulating bodies involved disagreed. Nothing to do with catching the grass on fire by the sides of a runway or the outboard engines being so far from the centerline of the aircraft.

Re: Quad engines and reverse thrust use

Posted: Wed Apr 17, 2019 11:32 pm
by Starlionblue
I’ll add that there is a thrust reverse lever for every engine so you can definitely use reverse only on one engine, for example.

Re: Quad engines and reverse thrust use

Posted: Thu Apr 18, 2019 12:00 am
by ChrisKen
The answer is a mix of all the above:
Airbus didn't want to include any during the design phase due to increased weigh and maintenance cost. The FAA objected and insisted it had a pair so Airbus obliged.
The pair are on the inboard engines, as they are closer to the centre line and therefore cause less issues with asymmetric ops and a large reduction in FOD risk that comes with being on the outboard pair.

In short, they had to include a pair to keep the FAA happy, the inboard engines are the logical choice.

Re: Quad engines and reverse thrust use

Posted: Thu Apr 18, 2019 1:08 am
by stratclub
Starlionblue wrote:
I’ll add that there is a thrust reverse lever for every engine so you can definitely use reverse only on one engine, for example.

I have a question about that. On a quad engine aircraft if one engine T/R is locked out would the same position T/R on the other wing be locked out as well, or would the pilot just compensate for yaw that occurs away from the locked out T/R with rudder, steering and brakes?

A graphic of a quad airplanes thrust levers to add a visual to your reply. the upper row knobs are for reverse thrust and the lower set of knobs are for forward thrust. There is an interlock that prevents the forward thrust and reverse thrust levers from being moved at the same time. Also the interlock locks out the reverse thrust levers if the aircraft is not firmly planted on the runway.
Image

Re: Quad engines and reverse thrust use

Posted: Thu Apr 18, 2019 2:25 am
by strfyr51
ALTF4 wrote:
I'm not an A380 pilot, so I am open to being corrected here. However, my understanding is that the pilots can command reverse on whichever engines they desire. On Boeing aircraft, for example, that would involve only engaging the reverse levers for the engines they wish to use.

Additionally, maintenance could "lock out" the thrust reverse actuators on the engines, preventing them from being used even when commanded. Unsure if this is an issue if commanded but "locked out"; e.g. does it actually still attempt to engage reverse or if the FADEC sees that and blocks it.

Finally, some aircraft don't have reverse thrust on all engines... and, in fact, this is the case on the A380 - so what you saw happen is entirely normal. ;-)

from what I've read, Because of how far out the outboard engines are on an A380, only the inboard engines are used to reverse thrust, I've only seen them land at SFO so it might not be indicative of what they can do. And since I'm retired now, Unless somebody is willing to pay me a salary that I can't refuse? I doubt I might be going back to work again.

Re: Quad engines and reverse thrust use

Posted: Thu Apr 18, 2019 2:28 am
by Max Q
stratclub wrote:
Starlionblue wrote:
I’ll add that there is a thrust reverse lever for every engine so you can definitely use reverse only on one engine, for example.

I have a question about that. On a quad engine aircraft if one engine T/R is locked out would the same position T/R on the other wing be locked out as well, or would the pilot just compensate for yaw that occurs away from the locked out T/R with rudder, steering and brakes?

A graphic of a quad airplanes thrust levers to add a visual to your reply. the upper row knobs are for reverse thrust and the lower set of knobs are for forward thrust. There is an interlock that prevents the forward thrust and reverse thrust levers from being moved at the same time. Also the interlock locks out the reverse thrust levers if the aircraft is not firmly planted on the runway.
Image



No, even with the yaw induced by having more reverse on one side you’re not going to lock out reverse on the other and lose even more stopping power


With uneven reverse thrust you’ll be more judicious in using it and compensate for
yaw with rudder, nosewheel steering and differential braking as needed

Re: Quad engines and reverse thrust use

Posted: Thu Apr 18, 2019 4:43 am
by stratclub
Back in the day, one of our old tired 707's had a habit of occasional having a T/R that would lock up and fail to deploy properly. I was in the observers seat on a test flight when we landed and one of the T/R's locked up making reverse thrust unavailable on that engine. The old salt pilot took it in stride and his only remark was "this plane flies a lot like a bicycle with loose handle bars".

The maintenance fix was to beat the clamshells back open with a 2X4 and run some mineral oil through the T/R's pneumatic lines with shop air while cycling the T/R a few times and the plane was good to go until the next time a T/R locked up. We had at one time, 17 of these old junkers with maybe 8 flying at any given time and with our mediocre maintenance, we never had an incident of any real significance. Certainly is a tribute to what a great plane the 707 was.
https://en.wikipedia.org/wiki/Aeroamerica

Re: Quad engines and reverse thrust use

Posted: Thu Apr 18, 2019 5:00 am
by Max Q
stratclub wrote:
Back in the day, one of our old tired 707's had a habit of occasional having a T/R that would lock up and fail to deploy properly. I was in the observers seat on a test flight when we landed and one of the T/R's locked up making reverse thrust unavailable on that engine. The old salt pilot took it in stride and his only remark was "this plane flies a lot like a bicycle with loose handle bars".

The maintenance fix was to beat the clamshells back open with a 2X4 and run some mineral oil through the T/R's pneumatic lines with shop air while cycling the T/R a few times and the plane was good to go until the next time a T/R locked up. We had at one time, 17 of these old junkers with maybe 8 flying at any given time and with our mediocre maintenance, we never had an incident of any real significance. Certainly is a tribute to what a great plane the 707 was.
https://en.wikipedia.org/wiki/Aeroamerica



Great stuff, and a fine tribute to a legendary aircraft

Re: Quad engines and reverse thrust use

Posted: Thu Apr 18, 2019 10:31 am
by Legs
Max Q wrote:

No, even with the yaw induced by having more reverse on one side you’re not going to lock out reverse on the other and lose even more stopping power


Funny, for the large quad I work on (albeit a military one), the book dictates that if one thrust reverser is inoperative, its symmetric paired engines reverser must be locked out, with an adjustment to the landing roll.

Re: Quad engines and reverse thrust use

Posted: Thu Apr 18, 2019 11:42 am
by Max Q
Legs wrote:
Max Q wrote:

No, even with the yaw induced by having more reverse on one side you’re not going to lock out reverse on the other and lose even more stopping power


Funny, for the large quad I work on (albeit a military one), the book dictates that if one thrust reverser is inoperative, its symmetric paired engines reverser must be locked out, with an adjustment to the landing roll.



That’s interesting, I’ve never seen that in the civilian airline world, of course as most
jet transports are twins these days if you lock out the other engine reverse you then have none at all !


Curious to know what type that is ?

Re: Quad engines and reverse thrust use

Posted: Thu Apr 18, 2019 11:55 am
by fr8mech
Legs wrote:

Funny, for the large quad I work on (albeit a military one), the book dictates that if one thrust reverser is inoperative, its symmetric paired engines reverser must be locked out, with an adjustment to the landing roll.



4 installed, 3 required on the B747.

Re: Quad engines and reverse thrust use

Posted: Thu Apr 18, 2019 12:29 pm
by Legs
Max Q wrote:
Legs wrote:
Max Q wrote:

No, even with the yaw induced by having more reverse on one side you’re not going to lock out reverse on the other and lose even more stopping power


Funny, for the large quad I work on (albeit a military one), the book dictates that if one thrust reverser is inoperative, its symmetric paired engines reverser must be locked out, with an adjustment to the landing roll.



That’s interesting, I’ve never seen that in the civilian airline world, of course as most
jet transports are twins these days if you lock out the other engine reverse you then have none at all !


Curious to know what type that is ?


C-17

Re: Quad engines and reverse thrust use

Posted: Thu Apr 18, 2019 1:35 pm
by SheikhDjibouti
Bluddy typical!
It's always down to me to remember the "other quads"..... :lol:

The Vickers VC-10 started out with four thrust reversers, but some years later the in-board T/Rs were removed.

The Ilyushin Il-62 only ever had T/Rs on the outboard engines, and made a habit of deploying them before touchdown. :twisted:

There are about a dozen photos showing T/Rs deployed before landing, but I thought these two were the pick of the bunch.



If you want to delve into tri-jets, the Trident used T/R in flight for up to 10,000 feet/min rapid descent rate (all three engines I believe), whilst the Yak-40 only has T/R fitted to the center engine and like the Il-62, often deploys it before landing (see below)

Re: Quad engines and reverse thrust use

Posted: Thu Apr 18, 2019 2:59 pm
by GalaxyFlyer
Legs wrote:
Max Q wrote:
Legs wrote:

Funny, for the large quad I work on (albeit a military one), the book dictates that if one thrust reverser is inoperative, its symmetric paired engines reverser must be locked out, with an adjustment to the landing roll.



That’s interesting, I’ve never seen that in the civilian airline world, of course as most
jet transports are twins these days if you lock out the other engine reverse you then have none at all !


Curious to know what type that is ?


C-17


That’s due to the blown flap arrangement and in-flight TR use.

Re: Quad engines and reverse thrust use

Posted: Thu Apr 18, 2019 7:51 pm
by BoeingGuy
stratclub wrote:
Airbus didn't want T/Rs at all, but the regulating bodies involved disagreed. Nothing to do with catching the grass on fire by the sides of a runway or the outboard engines being so far from the centerline of the aircraft.


What FAR or EASA requirement requires installation of thrust reversers?

The KC-46 is FAA certified and lacks thrust reversers.

Re: Quad engines and reverse thrust use

Posted: Thu Apr 18, 2019 8:21 pm
by zeke
BoeingGuy wrote:
What FAR or EASA requirement requires installation of thrust reversers?

The KC-46 is FAA certified and lacks thrust reversers.


Don’t know, but the FAA insisted. On the A330/340 the FAA insisted on the installation of ARM and JETtISON buttons in the cockpit.

The Bae146 has no reverse either.

Re: Quad engines and reverse thrust use

Posted: Thu Apr 18, 2019 8:29 pm
by stratclub
BoeingGuy wrote:
stratclub wrote:
Airbus didn't want T/Rs at all, but the regulating bodies involved disagreed. Nothing to do with catching the grass on fire by the sides of a runway or the outboard engines being so far from the centerline of the aircraft.


What FAR or EASA requirement requires installation of thrust reversers?

The KC-46 is FAA certified and lacks thrust reversers.

The tanker is built to military specs and it is not uncommon for military aircraft to not have T/Rs.

IDK the exact FAA requirement without making my head hurt by reading the FAR's. Look in volume I or II here: https://www.ecfr.gov/cgi-bin/text-idx?c ... tab_02.tpl

Re: Quad engines and reverse thrust use

Posted: Thu Apr 18, 2019 8:38 pm
by stratclub
zeke wrote:
BoeingGuy wrote:
What FAR or EASA requirement requires installation of thrust reversers?

The KC-46 is FAA certified and lacks thrust reversers.


Don’t know, but the FAA insisted. On the A330/340 the FAA insisted on the installation of ARM and JETtISON buttons in the cockpit.

The Bae146 has no reverse either.

What do the ARM/JETTISON buttons do? In regards to jettisoning fuel maybe?

Re: Quad engines and reverse thrust use

Posted: Thu Apr 18, 2019 9:48 pm
by BoeingGuy
stratclub wrote:
BoeingGuy wrote:
stratclub wrote:
Airbus didn't want T/Rs at all, but the regulating bodies involved disagreed. Nothing to do with catching the grass on fire by the sides of a runway or the outboard engines being so far from the centerline of the aircraft.


What FAR or EASA requirement requires installation of thrust reversers?

The KC-46 is FAA certified and lacks thrust reversers.

The tanker is built to military specs and it is not uncommon for military aircraft to not have T/Rs.

IDK the exact FAA requirement without making my head hurt by reading the FAR's. Look in volume I or II here: https://www.ecfr.gov/cgi-bin/text-idx?c ... tab_02.tpl


The KC-46 has full ATC and STC certifications with the FAA. It complies with all the same regulations as commercial airplanes. It’s not correct to say it’s built to military specs. It’s a 767 derivative modified after ATC cert
with military equipment.

It would be held to the same thrust reverser and stopping requirements as any other FAA certified airplane.

Re: Quad engines and reverse thrust use

Posted: Thu Apr 18, 2019 9:48 pm
by tu204
On the IL-76 (classic, not sure about the versions with PS-90 engines) although you have TR's on all four engines, you normally only use your outboard (Engines 1 and 4) reversers. That is unless shit hits the fan and your options are overrunning the runway or using reverse on all four (short runway, INOP outboard reversers or just a cockup by the flight crew)...

Two reasons:
1) Using inboard reversers you disrupt airflow to the outer engines and risk them surging/flaming out.

2) The way those buckets open you also blast the cowlings of the outboard engines with the redirected airflow. Next time you have the pleasure of seeing an IL76 up close, have a look at the inboard facing side of the outboard engines (between the respective engines on each wing). Notice dents on those outboard engines.

See the way the buckets are directed? Keep in mind the wing sweep and you should get what I mean.

Re: Quad engines and reverse thrust use

Posted: Thu Apr 18, 2019 10:22 pm
by stratclub
BoeingGuy wrote:
stratclub wrote:
BoeingGuy wrote:

What FAR or EASA requirement requires installation of thrust reversers?

The KC-46 is FAA certified and lacks thrust reversers.

The tanker is built to military specs and it is not uncommon for military aircraft to not have T/Rs.

IDK the exact FAA requirement without making my head hurt by reading the FAR's. Look in volume I or II here: https://www.ecfr.gov/cgi-bin/text-idx?c ... tab_02.tpl


The KC-46 has full ATC and STC certifications with the FAA. It complies with all the same regulations as commercial airplanes. It’s not correct to say it’s built to military specs. It’s a 767 derivative modified after ATC cert
with military equipment.

It would be held to the same thrust reverser and stopping requirements as any other FAA certified airplane.

Well ya. Boeing takes what they call a "Green airplane" and modifies it to military requirements with some of the mod changes incorporated during production. By the time it's airworthness certificate has been granted, yes you can say it was built to military spec because part of the built process is the mod work towards the airplane's as delivered config. You can have your pepper shaker back now...............

Re: Quad engines and reverse thrust use

Posted: Fri Apr 19, 2019 2:04 am
by BoeingGuy
stratclub wrote:
BoeingGuy wrote:
stratclub wrote:
The tanker is built to military specs and it is not uncommon for military aircraft to not have T/Rs.

IDK the exact FAA requirement without making my head hurt by reading the FAR's. Look in volume I or II here: https://www.ecfr.gov/cgi-bin/text-idx?c ... tab_02.tpl


The KC-46 has full ATC and STC certifications with the FAA. It complies with all the same regulations as commercial airplanes. It’s not correct to say it’s built to military specs. It’s a 767 derivative modified after ATC cert
with military equipment.

It would be held to the same thrust reverser and stopping requirements as any other FAA certified airplane.

Well ya. Boeing takes what they call a "Green airplane" and modifies it to military requirements with some of the mod changes incorporated during production. By the time it's airworthness certificate has been granted, yes you can say it was built to military spec because part of the built process is the mod work towards the airplane's as delivered config. You can have your pepper shaker back now...............


Yes but all of the military stuff is STC to FAA cert requirements, with the exception of a few systems that were contractually agreed to by Boeing and the USAF to follow a Military Type Cert.

Anyway that wasn’t my original point. My point was there must not be an FAA requirement for thrust reversers since the KC-46 holds an FAA ATC and STC and doesn’t have them.

I don’t get the pepper reference.

Re: Quad engines and reverse thrust use

Posted: Fri Apr 19, 2019 2:41 am
by zeke
BoeingGuy wrote:

Yes but all of the military stuff is STC to FAA cert requirements, with the exception of a few systems that were contractually agreed to by Boeing and the USAF to follow a Military Type Cert.


This is not true, the KC-46A tanker is not FAA certified, the base 767-2C is. Refer to the TCDS note 19 on the requirements to make a KC-46A back into a 767-2C. There is no FAR that covers air to air refuelling systems.


BoeingGuy wrote:
I don’t get the pepper reference.


A bit like when you call a company in the US, for English press 2.

Re: Quad engines and reverse thrust use

Posted: Fri Apr 19, 2019 3:06 am
by BoeingGuy
zeke wrote:
BoeingGuy wrote:

Yes but all of the military stuff is STC to FAA cert requirements, with the exception of a few systems that were contractually agreed to by Boeing and the USAF to follow a Military Type Cert.


This is not true, the KC-46A tanker is not FAA certified, the base 767-2C is. Refer to the TCDS note 19 on the requirements to make a KC-46A back into a 767-2C. There is no FAR that covers air to air refuelling systems.


BoeingGuy wrote:
I don’t get the pepper reference.


A bit like when you call a company in the US, for English press 2.


Well it is true. I worked on the program for 8 years. Remember when I mentioned that some systems are MTC? You are correct about the refueling system not being certified under ATC or STC.

Also, as far as the FAA is concerned, there is no such thing as a KC-46, which I think is what you were also stating. It’s a 767-2C and a Military Modified 767-2C.

Re: Quad engines and reverse thrust use

Posted: Fri Apr 19, 2019 4:23 am
by stratclub
Sorry. Picking fly "stuff" out of the pepper. If you consider all of the certification twists and turns the KC-46 is delivered as it is built with modifications to the KC-46/767 type certificate with the KC-46/767 type certificate including any STC departures that are required to meet the KC-46 airworthyness certificate. When the air force takes delivery of the aircraft, the only thing that matters is the as delivered config of the aircraft which is supported by Boeing engineering data.

Re: Quad engines and reverse thrust use

Posted: Fri Apr 19, 2019 4:31 am
by zeke
BoeingGuy wrote:
Also, as far as the FAA is concerned, there is no such thing as a KC-46, which I think is what you were also stating. It’s a 767-2C and a Military Modified 767-2C.


You are correct, the FAA call it a KC-46A, remember as I said refer to the TCDS.

‘KC-46A airplanes are tanker/cargo versions of the Model 767-2C. Prior to operation as a commercial aircraft, the following must be accomplished:
a) The maintenance, overhaul and modification records of each aircraft must be reviewed for changes made by the
military services that may affect the airworthiness of the aircraft. Modifications, changes of equipment and repairs,
which affect the safety or performance of the aircraft, must be approved by the FAA
b) All aircraft returned to civil operations must comply with all applicable Airworthiness Directives
c) All items that are not FAA approved must be removed from the aircraft if they affect the safety or performance of the
aircraft.
d) Each deviation from the FAA approved type design as listed on FAA Form 8130-31 “Conformity Certificate – Military
Aircraft” that is required for civil certification must be corrected per FAA approved data.”

Re: Quad engines and reverse thrust use

Posted: Fri Apr 19, 2019 7:27 am
by Starlionblue
stratclub wrote:
zeke wrote:
BoeingGuy wrote:
What FAR or EASA requirement requires installation of thrust reversers?

The KC-46 is FAA certified and lacks thrust reversers.


Don’t know, but the FAA insisted. On the A330/340 the FAA insisted on the installation of ARM and JETtISON buttons in the cockpit.

The Bae146 has no reverse either.

What do the ARM/JETTISON buttons do? In regards to jettisoning fuel maybe?


ARM arms the jettison system.
JETTISON starts the jettison.

Used in reverse to stop the process.

I have no idea why two pushbuttons are needed. Seems like one would be enough but I didn't design the aircraft. They're both red guarded pushbuttons so you're not going to press one by mistake.

Re: Quad engines and reverse thrust use

Posted: Fri Apr 19, 2019 2:48 pm
by BoeingGuy
Starlionblue wrote:
stratclub wrote:
zeke wrote:

Don’t know, but the FAA insisted. On the A330/340 the FAA insisted on the installation of ARM and JETtISON buttons in the cockpit.

The Bae146 has no reverse either.

What do the ARM/JETTISON buttons do? In regards to jettisoning fuel maybe?


ARM arms the jettison system.
JETTISON starts the jettison.

Used in reverse to stop the process.

I have no idea why two pushbuttons are needed. Seems like one would be enough but I didn't design the aircraft. They're both red guarded pushbuttons so you're not going to press one by mistake.


There’s very much a reason why there are two switches for Fuel Jettison, at least on Boeing airplanes. It’s intentional that it requires two separate actions for such a critical function. The Jettison Switches are guarded and surrounded by a red stripe, as you indicate, but the Arm Switch is an additional layer of protection.

Re: Quad engines and reverse thrust use

Posted: Fri Apr 19, 2019 3:45 pm
by stratclub
Thanks guys. that answers my question. My assumption the dialog was about the fuel jettison system is correct then. It certainly would be a bad day to be half way across the Atlantic and have your center tanks low pressure lights come on because you had inadvertently been jettisoning fuel.

Re: Quad engines and reverse thrust use

Posted: Sat Apr 20, 2019 12:04 am
by Starlionblue
BoeingGuy wrote:
Starlionblue wrote:
stratclub wrote:
What do the ARM/JETTISON buttons do? In regards to jettisoning fuel maybe?


ARM arms the jettison system.
JETTISON starts the jettison.

Used in reverse to stop the process.

I have no idea why two pushbuttons are needed. Seems like one would be enough but I didn't design the aircraft. They're both red guarded pushbuttons so you're not going to press one by mistake.


There’s very much a reason why there are two switches for Fuel Jettison, at least on Boeing airplanes. It’s intentional that it requires two separate actions for such a critical function. The Jettison Switches are guarded and surrounded by a red stripe, as you indicate, but the Arm Switch is an additional layer of protection.


The idea that you might inadvertently jettison fuel from a single guarded pushbutton seems far fetched to me. I can't see how you would unintentionally open a red guard, then unintentionally press a pushbutton. That's already two separate actions. (Then you have to miss the jettison message on the screen.)

FIRE cutoff, IDG disconnect and RAT MAN ON are all single guarded pushbuttons. Why has jettison been singled out with two separate pushbuttons when you can cut off all the feeds to an engine with one?

I'm sure there's a specific reason for this setup. I just don't know exactly what it is.

Re: Quad engines and reverse thrust use

Posted: Sat Apr 20, 2019 12:24 am
by zeke
Exactly, the only reason Airbus had to change their panel was because Boeing did it that way.

May have had more relevance when there was a flight engineer, however with the automatic jettison stop it makes no sense.

Re: Quad engines and reverse thrust use

Posted: Sat Apr 20, 2019 7:05 am
by AirlineCritic
ChrisKen wrote:
The FAA objected and insisted it had a pair so Airbus obliged.


That's interesting, I didn't know this.

(As an aside, maybe it is time for the rest of the world to insist that if there are flight augmentation systems in the 737MAX with catastrophical failure modes they be built to use three sensors and 2-out-of-3 redundancy. And that efficacy of manual trim be re-analyzed and re-flight tested, and practiced in the SIM for every pilot.)

Re: Quad engines and reverse thrust use

Posted: Sat Apr 20, 2019 7:31 am
by Starlionblue
AirlineCritic wrote:
ChrisKen wrote:
The FAA objected and insisted it had a pair so Airbus obliged.


That's interesting, I didn't know this.

(As an aside, maybe it is time for the rest of the world to insist that if there are flight augmentation systems in the 737MAX with catastrophical failure modes they be built to use three sensors and 2-out-of-3 redundancy. And that efficacy of manual trim be re-analyzed and re-flight tested, and practiced in the SIM for every pilot.)


I'm amazed the FAA didn't insist from the start!

Re: Quad engines and reverse thrust use

Posted: Sat Apr 20, 2019 9:53 am
by zeke
Starlionblue wrote:
[
I'm amazed the FAA didn't insist from the start!


Two sensors can fail, eg bird strike on one side and drop out the good AOA on the other side.

Better widgets don’t make better pilots.

Re: Quad engines and reverse thrust use

Posted: Sat Apr 20, 2019 3:00 pm
by GalaxyFlyer
2 out of 3 has failed due to icing on a an Airbus 320, maybe 3 out of 5 or 4 out of 7.

GF

Re: Quad engines and reverse thrust use

Posted: Sun Apr 21, 2019 12:39 am
by Starlionblue
zeke wrote:
Starlionblue wrote:
[
I'm amazed the FAA didn't insist from the start!


Two sensors can fail, eg bird strike on one side and drop out the good AOA on the other side.

Better widgets don’t make better pilots.


Indeed. What I meant was that for this type of system, triple redundant sensing would seem like the minimum requirement in a modern aircraft.

Plus training. And discrepancy warnings.

Re: Quad engines and reverse thrust use

Posted: Sun Apr 28, 2019 4:49 am
by Apprentice
On old Il62M, 4 aft fuselaje Engines, Reverse On 1, and 4.
On approach, all level in idle. Reverses Handle On (1 handle)
With every thing ok, FE accelerated eng 1/4 and use to s/d 2/3
Rgds

Re: Quad engines and reverse thrust use

Posted: Sun Apr 28, 2019 12:29 pm
by tu204
https://youtu.be/2z0ek-8YODs

Checked some videos.
The IL-76 with PS-90's uses reverse on all 4 engines as standard.

So the reason for not using inboards on the classic was strictly related to where the buckets redirected the flow to.