Testing of idle reverse thrust before takeoff. A wise precaution?
 

https://avherald.com/h?article=4c5b3f3d&opt=0

An A320 lands and reverse thrust fails to operate. There had been no prior warning flags in the cockpit. Maintenance staff had forgotten to remove the reverser lockout pins after servicing. The situation could have been critical if a high speed rejected takeoff occurred at the departure airfield and the crew were unaware the reversers had been locked out.

System caution lights have removed the once good airmanship requirement of the momentary testing of brakes after moving from the tarmac. However, the above incident illustrates that on this occasion a fault in reverser operation did not show up to the cockpit crew until too late

A short test of reverse idle at an appropriate point before takeoff would have revealed this maintenance defect.. Another cue for good airmanship?
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But could be a seriously big deal on a high speed rejected take off if runway limited..

A thought

The plane is certified to stop safely with the reversers locked out.

Give a thought to how many tasks you want to perform over and above what's in the manuals

Just in case I would also check the spoilers movement, and check the engines are getting up to toga thrust should I need it, and also check the flaps travel down to 3 if I need to come back quickly and also I would close manually the outflow vale and pressurise the plane to check it does pressurise. Anyway short answer to the above : no, it's not, as performance data is there for you to consider a no reverse situation up to a contaminated runway.

I agree with most of the posters here: it’s not a major issue 99.99% of the time should they not deploy, plus static use of of thrust reversers is not helpful in terms of FOD and/or surging. After all, if you’re going to check they work properly that involves full reverse...

Forty+ years ago on the B707-436 with R-R Conway engines reverse was indeed checked on taxy out. Try that with a JT3D powered aircraft and you will be in a whole world of pain!

On dry runways the effect of REV is not taken into account for PERF calculations. The scenario you fear is (all need to apply at the same time)
- wet runway or worse
- ASDA limited take-off
- RTO at V+-10 to V1

The chances are very remote. For what is left, the standard walk around check of REV lock-out pins should cover. No need to envisage new procedures where at least 50% compliance with the present ones would do. Agreed?

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although from the report: https://www.atsb.gov.au/media/577576...-064_final.pdf
it is not clear whether the standard pin as seen here https://www.atsb.gov.au/media/577576...-064_final.pdf was visible on the outside of the casing.

Now, the paragraph "AMM specific wording of HMU deactivated ..." of the report is the funny part.

Highly visible lock out pins should have been caught on even the most cursery walkaround.

The HCU is under the pylon on left side underneath the cowling, it isn't visible externally so can't detect incorrect HCU config during walk-around.

There is a streamer-free pin that lives up there and stays with the aircraft. that is what the engineers used to lock out the reversers and forgot to remove.

Very sloppy maintenance. If I'm not mistaken, landing performance is predicated on braking action with nil reverser credit? (I'm not a pilot).

Correct. The only difference is that, in case of landing on a contaminated runway, You need to take it into account from a performance point of view (i.e. add the impact of a no reverser configuration).

Thanks sonicbum. I forgot to ask. Would the takeoff run be the same?

Just follow SOPs
 

I agree with the ‘not a good idea’ crowd.

Also on every Boeing I’ve flown selecting REV on the ground deletes all your Vspeeds from the FMC.

Keep It Simple, just follow manufacturer and company SOPs.

The willingness not to, as alluded to by some of the questions on this forum, do make me worry about my fellow aviators.

Global Express, Citations, I suspect Gulfstreams too. Never seen in done on modern airliners though

Never tired of saying don't make your own procedures. If too tempted ask the manufacturer. This becomes an addiction. And on aircraft run on software can have other effects which are not obvious.

I was not aware of that on the BOAC RR 707's, but if you open the reversers on a PW JT3D they have fan cold and hot end sliding cowls, and very often one would not fully close up after landing.
The RR engine on the 707 had cascade type reverser built by RR
(the DC8 43 Conway application was different with a Douglas transiting ring thrust reversers and exhaust silencers)

Reject executed at V1 will only give you a 50% chance of stopping in the remaining distance anyway

Its calculated using Gross not Net data.

You wouldn't like to expand on these points, would you ?

Thrust reversers fail to deploy for a number of reasons - the numbers are better now than they used to be, but figure roughly once in every 5,000 to 10,000 deployments a T/R will fail to properly deploy due to some fault, and someone forgetting to remover the lockout pins is pretty low on the probability list of failures.
As VinRouge notes, deploying the T/R prior to every takeoff just wears them out quicker, and makes it a little more likely one will fail when you really need it.
Besides, what are you going to do if one fails to deploy on a pre-takeoff check? Most likely you're go to go back, take a delay while the T/R gets deactivated and locked out, then depart with a reverser that doesn't work - which is what you're would have done anyway except now you're doing it several hours later...

Checking reversers with the aircraft stationary at the end of the runway or on the taxiway not a good idea as the reversed exhaust gas flow could blow stones or any other FOD up which could get ingested into the fan or core and cause you an even more significant problem. Not sure what flight crew operating procedures say about stowing reversers on landing at what speed to prevent this (and I'm pretty sure you don't use T/Rev to come to a complete stop), but as an Engineer we do not usually carry out an engine running reverser check on ramp for this reason. We usually have a facility through the CMS to do a cycling check using electrics or hydraulics. I can only speak for what I work on (Airbuses and B744), and there could be exceptions to this.......and yes I do know cascade vanes are designed to mitigate the ingestion of blown up FOD, but still good practice I'm sure.

Not really......

A37575, you have to remember that there is very little, if any, reverse thrust. Most reversers only affect the fan air, not the flow from the core. Whilst the fan flow might generate some reverse, the core is still pushing you along. All reverse really does in an airliner is cancel out the core thrust, and not much more. It does destroy the lift generated by the wings and may dissipate any water that might be on the runway - both help sit the aircraft down on the ground a bit more firmly - but that's about it.

Well, the ground crew will love you, after they finish picking everything up.

The above argument would suggest having a reverse thrust system at all is a very expensive exercise in poor cost effectiveness. Why haven't the manufacturers realized this and built their aircraft without reverse thrust? Save millions of $$$ in maintenance costs. OK - reverse might be handy on slippery runways when wheel braking efficiency is reduced but it could be cost effective to accept that risk.:ok:

Almost all of the thrust generated by a large turbofan comes from the fan, so it's illogical to suggest that the absence of a core reverser makes much difference.

Early RB211s, for example, had both but the core reverser was subsequently deleted because it was a PITA for very little benefit.

Centaurus,
Look at the A380 - only reversers on #2 & #3. Just enough to claim the "major means of deceleration" for certification but really a WOFTAM.
The concept of testing reverse thrust prior to each takeoff is simply risible - where do you stop testing? Reversers and brakes worked fine last landing or there would be a tech log entry so just fly the aircraft FFS and not try to do block overhaul each T/R.

Not sure if this true or not but heard it few times now......the A380 was originally designed with no T/Rev, but it was the regulators who said that it had to have it as the design spec for that standard of aircraft dictated it and so it was installed on the inboards to satisfy them.

80% of a modern, high by-pass engine's thrust comes from the fan. The core engine is really only there to drive the fan, the gearboxes for the ancillary pumps/generators etc. , and provide bleed air for air conditioning/anti-icing. On that basis Fan T/Rev thrust significantly cancels out Core Thrust during application of of T/Rev.

All true and revisited years ago in regulatory discussions.

In the end there was a realization that there was a money making business to offer the pilots what they wanted

Re post #34, Airbus once proposed at one of the A3XX airline working groups back in the 1990's to delete all thrust reversers to save weight and complexity however the airline working group recommended at least 2 engines have reversers. The main reason for rejecting the no reverser proposal was the estimated required runway length at MTOW for a slippery/contaminated runway if I recall correctly..

A reverser test after maintenance seems to makes sense -- by someone at least. One of the major missteps in the the report was that the engineers skipped a required functional test. Of course, that doesn't mean that the flight crew should repeat it just in case . . .

I know....