Commenting on PRs with suggested improvements is a big win to reduce the context switching senior engineers face reviewing junior developers PRs all day, giving a review complexity rating that can be used to route PRs to the right people is good as all. Of course being open source, platform agnostic is a massive win.
One idea I had was if there was an optional dashboard overview across all the repos it's enabled on where users could directly trigger / interact with specific PRs or issues - that would be neat.
Oh something else great it has - you can run it locally against any repo or branch, great for testing or pre-commit hooks.
It looked neat but relies on a cloud db called 'TIDB', I checked its repo out and it looks like you can self host that as well but damn - it's a lot of containers. So yeah looks like self hosting is an option but likely a pain in the ass.
- Where is the source code? This is critical for it to be inspected before adding to any repos.
- What models are you using?
- Where are the models running?
- When you say it learns from your codebase is it building a RAG or similar database or are you fine tuning from other people's code?
The service runs on secure cloud infrastructure and processes code in-memory during PR reviews - we don't permanently store any source code. We use enterprise-grade LLMs (can't disclose specific models due to licensing) and implement context-aware analysis without fine-tuning on customer code.
When we say "learning", we mean analyzing the codebase context during PR reviews to understand patterns and relationships, not training or building persistent knowledge bases. This ensures both privacy and effectiveness.
We're working on open-sourcing parts of the implementation - will share more soon!
I was speaking with a 787 pilot last Sunday, I told him that the week before when I was at an airport there were two pilots sitting next to me talking about how "This is the third bloody 787 rescue we've had this month... I can't believe we had full engine and <I think he said auxiliary?> failure at the same time" - I asked him if this is common and he said "I hear of it, but I haven't had that many major failures, but lots of little things - last time I flew in from <city> a few moments after we touched down we lost auxiliary power from the rear engine, all the cabin lighting went black along with a number of other things, thankfully we'd already significantly reduced speed and were straight and already lost most of the speed we were carrying, so we were fine and taxied to the disembark location, they had it up and flying again within the day - but it certainly was disconcerting to say the least".
I will be slightly paraphrasing from memory there, but certainly was quite surprised how calm he was about the whole thing, there's no way I'd board one of those things.
Modern two-engine planes like the 787 have an auxiliary power unit (APU) in the tail. This is a small turbine that runs a generator and a pump for the hydraulics. It’s typically only turned on when the plane is on the ground, or if there’s an emergency in mid-air. It is also needed to start the main engines so if the APU is faulty the plane will probably be stuck where it is. In theory a 787 can take off with just one engine but this is not very safe and wouldn’t be done in all but the most exceptional circumstances.
There are variations on this depending on the plane model, of course. Some older planes can use an external starter for their engines, but I think that’s very rare now.
Aircraft with INOP APUs can generally be "air started" with a ground-based high-pressure air system. It's relatively common and I've been on a plane that had to do the procedure. It was entirely undramatic other than engines being started before the pushback, but I doubt most passengers even noticed.
Now, interestingly, the 787 is a "bleedless" aircraft, so it doesn't use high-pressure air from the APU to spool up the engines. I believe it can use its hefty bank of lithium-ion batteries to start its engines if the APU (and associated electrical generator) is INOP.
Not a pilot/engineer - just an enthusiast. Someone more au fait with the 787 might be able to correct me on the above.
My understanding is that there was a push to modify the U shaped tow trucks they use to position planes to have a battery powered system to start the engines.
The idea being that the APU isn't particularly clean burning, not compared to power plant emissions. It's been a long while since I've heard anything about that plan, for or against.
Interesting! Although it'd (presumably) only be useful for the 787, short of heavy modification to existing aircraft. Even the Airbus A350, an aircraft from the same era, uses a traditional bleed system. If planes continue down the bleedless route I can see it happening.
>Modern two-engine planes like the 787 have an auxiliary power unit (APU)
Where "modern" here includes jet airliners made in the 70s yes.
>It is also needed to start the main engines
The engines need an air source, and the APU can be an air source, but at one point at least, big airlines preferred using ground hookup provided air sources for starting, in order to save gas. Next time you fly, look at the jetway. There will be a large yellow duct system underneath it that can be hooked up to the plane to provide pneumatic pressure and air conditioning air without starting the APU. There are similar hookups for electrical power so that a plane won't drain its battery during routine turnover operations.
The bottom price flights I've taken recently don't seem to hook either up though, preferring instead to start the APU during taxi to the gate while shutting down one engine, shut down the other engine once they are at the gate, and reverse the process to taxi back out to the runway. The turnaround time is so short, and the required work to clean and restock the cabin so little, I bet they just don't pay for ground hookups.
There is also a RAT at the back that can be deployed to generate some power(~5-10 minutes max) in case of severe emergency in Air. It is what you hear sometimes, when the aircraft is making a very shrill noise flying over your head.
However, if it is not a test flight, a RAT deployment should make you very uncomfortable and worried…
> RAT … It is what you hear sometimes, when the aircraft is making a very shrill noise flying over your head.
I’ve been around a lot of airplanes and I can’t say I’ve seen or heard a ram air turbine deployed in flight. There was a recent incident involving a Frontier Airlines flight in which the RAT was deployed when the aircraft was put in emergency electrical configuration. The deployment of the RAT would be quite rare.
I find it hard to believe that anyone reading this was within earshot of a plane in a severe emergency and heard this particular sound and since turbine engines are already quite shrill I am basically just sorta confused who your audience is for this suggestion.
Usually, when the RAT is really deployed because of an emergency, the jet engines will be a lot more silent (because they're not producing any power). Although I'm not really sure how loud a windmilling jet engine really is, and I somehow doubt there is a YouTube video of a plane landing with both engines disabled - but you never know...
Would you hear it from inside the plane? Even if it’s not as loud as the main engine, if it’s audible at all a lot of people would notice a change in pitch/tone. At least, I notice when the sounds the plane is making change even though I don’t know anything about the reason.
> After starting the descent, the flight crew made an announcement to the passengers; however, unbeknownst to the flight crew, the noise generated by the RAT (because of its high rotation speed) prevented the passengers and the cabin crew from hearing the announcement.
It always surprised me that there aren’t small, local lithium batteries to provide backup power for critical components like the smoke detectors. Is the risk of those catching fire considered too high?
>It always surprised me that there aren’t small, local lithium batteries to provide backup power for critical components like the smoke detectors
There is, well, only lithium on the 787. If all power generation is dead, then the most critical flight instruments and gauges get about 20-30 minutes of power from the plane's batteries, things like your backup old fashioned gauges, the engine computers, and maybe some basic flight computer on newer planes. The RAT is intended to keep flight surfaces operational when everything else is utterly fucked, so it usually produces the same kind of energy as whatever the primary flight control system uses, which until recently was hydraulic power. On civilian airliners they generate tens of kilowatts. Airliners do not want to carry around an EV sized battery for the extremely rare occasions when you lose all systems, because that's a waste of gas. The RAT provides the same functionality for lower weight.
When the RAT is deployed, you do not care much whether a smoke detector is powered, you are already vectoring towards an attempted landing.
I feel like it's not the RAT you'll notice from inside the plane, it will be the silence from the engines. That combined with at least a momentary flicker of the lighting (I'm not sure if a RAT on a 787 will run cabin lighting but I doubt it), and you'll know.
Haha I didn’t parse it that way but I can see how you thought that upon rereading. I just want to understand why we would hear the RAT when there wasn’t an emergency overhead. I supposed planes regularly test them?
I'm not going to bother slogging through everything to be able to speak in specifics for every airplane ever built, but:
A RAT provides backup electrical and/or hydraulic power for control surfaces (and other goodies). A RAT would certainly be inspected during a heavy check and likely even during line checks (e.g. an "A" check or equivalent). How often is gonna depend on the airplane. But to suggest that a critical piece of equipment isn't checked regularly is just silly.
Additionally, it's pretty much guaranteed that if an airplane comes with a RAT the RAT is required to be functional for ETOPS flights. That alone means you're gonna be inspecting it pretty frequently. ETOPS certification has three parts: airplane, airline, and humans. You'd want to look at the ETOPS Maintenance Document at whatever airline to be sure.
Outside of Asia (where domestic widebody flights are still common) I'd guess many if not most 787 flights are ETOPS flights.
> Additionally, it's pretty much guaranteed that if an airplane comes with a RAT the RAT is required to be functional for ETOPS flights. That alone means you're gonna be inspecting it pretty frequently.
I remember a decade or more ago I was on a US domestic flight - I forget exactly what, I think it was American from SFO to LAX - so I doubt it needed ETOPS. But the captain announced - while we were still at the gate - that he was getting an error in the cockpit saying the RAT was faulty. And he called maintenance, and they told him to try resetting something (a computer or circuit breaker or whatever) to see if that cleared the error - and when it didn’t, he announced we could not take off and would all have to go back into the terminal. Thankfully they had a spare plane a few gates over and they put us all on that (same crew, same passengers) so we only lost an hour or two.
Right. In the context of this discussion ETOPS buys you significantly increased inspection and maintenance requirements. That's why I don't playing this game of telephone. Someone told someone else that something else did something else. Were everything to have unfolded as transcribed here there almost certainly would've been a high profile investigation.
Back to your flight, both the FAA and EASA require airliners to have a minimum equipment list (MEL). It's entirely unrelated to ETOPS (overwater flights). This list describes what equipment is required to be functional, what you can fly without and when. What's on the list is all going to come down to what kind of plane we're talking about. Could be you're not allowed to fly without a functional RAT ever. Could be that you can fly without a RAT as long as something else (e.g. APU) is functional. Could be you can only make a certain number of flights with a non-op RAT.
A real world example is that ATR 72 crash in Brazil recently. One of the PACKs (air conditioning / cabin pressurization) was not functioning on the accident plane. Per the MEL you can dispatch an ATR in that condition, but you're limited to a service ceiling of 17,000 ft. Unfortunately that put the flight in direct conflict with the weather.
You’re right; my statement was in the context of the above discussion about people claiming to somewhat-regularly hear RATs in the air above them. That definitely isn’t happening.
But the turbine generates power to keep the plane flying. Why would it only work for 10 minutes? Certainly the flight time is a product of fuel level and altitude. Even if both engines fail the flight time would be a function of altitude. I don’t see how deployment of the RAT informs flight time.
It does not generate power to provide thrust; it generates power - using the airstream as the aircraft moves through the air - for the avionics and/or hydraulics.
/s? A generator or alternator powered directly by the engines is more efficient than towing a wind vane (still indirectly powered by the engines and/or the potential energy of the airplane) every single time.
This discussion has nothing to do with engine out failure modes.
I thought the guy I was speaking mentioned something about instrumentation but I wasn't 100% sure and that sounded more serious so didn't mention it - but if the aux engine failing would do that - I guess that lines up!
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