Reclearance in Flight

[Evan]

I thought it would be a good idea to start a thread on this and remove it from the AF447 thread, so anyone who wants to discuss the issue can do it here.

Reclearance in Flight (RIF) is a contingency against the trip fuel estimate in the case of unexpected fuel burn. In the absence of RIF, this is done through the variable reserve factored into the fuel order. For flights that involve a significant latter segment of their flight plan in the proximity of alternate airports, RIF offers a more operator friendly alternative that relocates the contingency for fuel from the aircraft to the ground, thus relieving the operator from the cost of flying unused fuel around and allowing them an opportunity for increased payload revenue.

The offset is that it raises the stakes for the operator in the case of higher than expected fuel burn, because a technical stop is far more expensive and disruptive than a diversion using reserves on any given flight (although I allow the possibility that it might lessen them when amortized over a large number of flights). Therefore, I would expect operators to use this option only when conditions seem favorable and the likelihood for needing the reclearance seems remote.

Now, the safety aspect. In any case, a provision against fuel starvation is provided, so that is a non-issue. The risk that I see is when pilots are forced to make a grey-area decision on diversion around potential weather threats (or any other decision that might incur greater fuel burn and affect safety). The reason I see this risk is due to an understanding of how both distinct and implied pressures influence the rationale and distort the perception of the human mind. I worry that the significant financial consequences of a technical stopover for fuel may dissuade certain crews from taking a more prudent course, and might promote marginal risk-taking, in these situations.

To be clear, I am referring to marginal threats, not clearly dangerous ones. I trust most pilots to avoid even marginal risks at any cost, but not all of them. I am also considering the cockpit authority gradient and I submit that, in reality, the gradient does not stop in the cockpit.

I also consider that pilots are very task-oriented, and the task is to complete the flight on schedule. When used in place of reserves, RIF negates that possibility.

I would like to be convinced otherwise, so I invite other points of view.

[Peter Kesternich]

To be clear, I am referring to marginal threats, not clearly dangerous ones. I trust most pilots to avoid even marginal risks at any cost, but not all of them.

I believe that it's difficult to categorize risks as marginal and dangerous. Where would you draw the line? Something marginal that eventually leads to an accident will then have turned into something dangerous. Taking this idea to the end (Caution! Hyperbole!) means that getting into an aircraft always involves the theoretical risk of a crash, and there is one guarantee in every person's life on this planet, that it will eventually lead to death (Hyperbole off!)

Willingness to take risks is something that is part of a person's character. There is of course the element of training and regulations that should help reduce the risk-taking in airline pilots. In the case of RIF it is clearly done through regulations - and beyond that, there is nothing much anyone can do about it. One could of course stop this practice altogether, but this will in my opinion not prevent an airliner from running out of fuel someday because the crew pressed on when they shouldn't have.

[Evan]

I believe that it's difficult to categorize risks as marginal and dangerous. Where would you draw the line? Something marginal that eventually leads to an accident will then have turned into something dangerous. Taking this idea to the end (Caution! Hyperbole!) means that getting into an aircraft always involves the theoretical risk of a crash, and there is one guarantee in every person's life on this planet, that it will eventually lead to death (Hyperbole off!)

Willingness to take risks is something that is part of a person's character. There is of course the element of training and regulations that should help reduce the risk-taking in airline pilots. In the case of RIF it is clearly done through regulations - and beyond that, there is nothing much anyone can do about it. One could of course stop this practice altogether, but this will in my opinion not prevent an airliner from running out of fuel someday because the crew pressed on when they shouldn't have.

When I say 'marginal', I mean the danger is not clearly defined. There is something there (a cluster of CB's with tops at FL55) but no definite threat to avoid (heavy precip, wind shear, electrical discharge etc.) and mitigating factors (previous traffic report benign conditions in the recent past). The risk is there, but it is conceivably a minor one. Now the crew must make a calculated decision based on what they know (and what they don't know) about the weather and the aircraft. What I'm getting at is, I don't want them to also factor into threat calculation the negative financial and logistical repercussions of avoiding it. Not even in a very back-of-the-mind, almost subconscious level.

NOTE: As I said in the beginning, I am NOT concerned with running out of fuel. That is not at all the threat I refer to.

[Peter Kesternich]

What I'm getting at is, I don't want them to also factor into threat calculation the negative financial and logistical repercussions of avoiding it. Not even in a very back-of-the-mind, almost subconscious level.

How do you suggest to free the pilots of that?

[Evan]

How do you suggest to free the pilots of that?

Abolish the RIF option, and require that all flights take on enough TOF to provide sufficient variable reserve for any reasonable diversion. (for more extreme diversions, a fuel emergency can always be declared and a technical stopover taken). Because the financial issue is in the fuel order, a requirement relieves the pilots from any company repercussions.

[Curtis Malone]

Although your post includes the words "to be clear", I remain unsure as to what your actual point is. Judging by your last post, you expect some greater amount of contigency fuel to be aboard each flight to (ostensibly) expand the diversion envelope, that is to say, increase the number of viable diversion points. Is that what you're saying or am I misunderstanding you completely?

I also confess that I don't belive I've ever heard the term "reclearance in flight". Reclearance to do what exactly?

[Evan]

Although your post includes the words "to be clear", I remain unsure as to what your actual point is. Judging by your last post, you expect some greater amount of contigency fuel to be aboard each flight to (ostensibly) expand the diversion envelope, that is to say, increase the number of viable diversion points. Is that what you're saying or am I misunderstanding you completely?

I also confess that I don't belive I've ever heard the term "reclearance in flight". Reclearance to do what exactly?

I'm suggesting the existing fuel requirements for non-RIF (DCT) flight plans are sufficient as they are, that the RIF option to reduce variable reserve requirements be abolished, and that technical stopovers should require a fuel emergency declaration. I'm open to the idea that this might not be any safer though, if you can convince me of that.

Reclearance to switch to the RIF flight plan filed in addition to the primary one.

[MCM]

Interesting idea Evan, but I hope you understand that it isn't just done to take a little extra freight - on a lot of occasions it is done because it would be not possible to depart with an economically viable load without it. And here I'm talking in the hundreds of passengers.

Forcing the declaration of a fuel emergency for any non-scheduled stop will DECREASE safety dramatically. The pressure on crew to not divert would be significant, and I think you'd find crew would be MORE inclined to save every drop of fuel to ensure that doesn't happen! Currently, it is recognised that the flight might have to technical stop, and so there is no pressure on the crew if they cannot continue. If you change to your proposal, the crew will be expected to make destination, and would be subject to investigation anytime they did not.

I think you are also underestimating how important to operations this is. If you choose to make aircraft carry fuel to the destination on every occasion, many operations would not be viable. Fuel reserve rules would change to allow these operations. Remember, safety isn't a threat here.

For about 50% of the year in Europe, the simple fact is that your flight would not be able to depart... and I can't see how thats a reasonable alternative. Launching with the possibility you might have to stop for fuel (based on a forecast for 14hrs time), and getting updated information closer to your arrival is a safe and sensible option.

Under your proposal there would be SIGNIFICANT (and I mean extremely significant) pressure on weather forecasters to forecast weather that is better than the alternate minima. The money involved in getting a favourable forecast would be unbelieveable (in the billions of dollars), and the possibility of aircraft being caught out from a deteriorating weather has a detrimental effect on safety.

I think I like it the way it is thanks.

[Peter Kesternich]

Quite a number of good arguments here, MCM, that I hadn't thought of when I asked what Evan's suggestion would be.

[Evan]

MCM, there is something I'm not understanding in your claim that some of these flight would not otherwise be possible. Do you mean not economically possible (commercially viable) or do you mean actually impossible?

I'm making some assumptions. I assume that when Airbus designed the A330 to fly at 233t, they factored in the average weight of passengers on a full flight at max configuration, their luggage and the weight of a full fuel order. I also assume that this criteria is the basis for giving the a/c its rated range estimate (as opposed to ferry range). I assume that this range estimate is based upon fuel to destination plus fixed reserve, under ideal conditions. As I've pointed out earlier, the GIG-CDG flight is far under this range, so the difference in distance vs. range would provide a generous margin for less than ideal conditions and minor diversions. It therefore seems logical to me that the only way this flight would not be possible without RIF is if the operator was also consigning a significant amount of freight as well. But you state that you are talking about shedding pax, not freight. Can you better explain this for me?

Forcing the declaration of a fuel emergency for any non-scheduled stop will DECREASE safety dramatically. The pressure on crew to not divert would be significant, and I think you'd find crew would be MORE inclined to save every drop of fuel to ensure that doesn't happen!

Yes, this crossed my mind. The thing to consider is that, under my proposal, fuel emergencies would only result from large diversions, which would signify a clearly dangerous threat, and I'm far less likely to doubt pilot judgment in those cases (and because the threat would be undeniable, the fuel emergency would thus be perfectly excusable). Remember, it's only the grey area, marginal threat decisions that concern me.

Also...

Currently, it is recognised that the flight might have to technical stop, and so there is no pressure on the crew if they cannot continue.

I have to disagree with you there, as I've stated in my original post. I suspect that the pressure to avoid the stopover is still present, and more so in marginal situations due to a lack of fuel reserves needed to make smaller diversions.

[Gabriel]

Evan, I'm not MCM, but let me give it a try:

I'm making some assumptions. I assume that when Airbus designed the A330 to fly at 233t, they factored in the average weight of passengers on a full flight at max configuration, their luggage and the weight of a full fuel order.

Nope. Typically an airplane full of pax, luggage and fuel will exceed the MTOW.

There are some famous charts that show range vs number of passengers (or payload).

For low payloads that let you fill the takns without exceeding the MTOW, the range diminishes somehow little for every additional pound of payload (or passenger), because each additional pound of payload adds one additional pound to the gross weight which requires an equivalent additional increase in lift which increases the drag (if the plane has an L/D=20, every 20 pounds of extra weight you have 1 extra pound of drag).

At some point you reach the MTOW. Now for every additional pound of payload you have to reduce one pound of fuel. The gross weight doesn't change, so you don't have the added drag penalty, but 1 pound of fuel less reduces the range more than 1/20 pounds of extra drag. So now every additional pound of payload has a strong effect reducing the range.

At some point you reach a payload that equals the MZFW (maximum zero fuel weight). You can't add any additional pound of payload after that even if you remove more fuel. Every pound of fuel you remove from this point is just a pound less of gross weight, with the corresponding loss in range.

I also assume that this criteria is the basis for giving the a/c its rated range estimate

As stated above.

I assume that this range estimate is based upon fuel to destination plus fixed reserve, under ideal conditions.

Typically, with IFR reserves, that is the fixed and the variable reserves, no wind, no weather detours, no ATC delays, ideal flight level, no alternate, ISA conditions.

When only the range is stated, as in a "spcification sheet" that is only a brochure in fact, add to the above full tanks at take-off. If not you have the forementioned chart.

When you look at the specifications of an airplane in Internet and see "Paylod x, range y", what you don't see is that x and y can't happen together. X is the payload with the plane at MZFW (maximum zero-fuel weight, which is the max you are alowed to load in the fuselage even if there is room for more weight before reaching MTOW), and Y is the range with full fuel and whatever payload you can put after that to reach the MTOW.

As I've pointed out earlier, the GIG-CDG flight is far under this range, so the difference in distance vs. range would provide a generous margin for less than ideal conditions and minor diversions. It therefore seems logical to me that the only way this flight would not be possible without RIF is if the operator was also consigning a significant amount of freight as well. But you state that you are talking about shedding pax, not freight. Can you better explain this for me?

On one hand, see above.

On the other hand, hold on a second: Are you talking about this AF flight in particular? I thought there was another thread for that and that this thread was to discuss RIF in general, where certainly what MCM says can be true regardless of whether it applied to this AF flight or not.

[Evan]

OK, that's news to me. I always assumed that the aircraft could carry full fuel tanks and a full passenger load, and the airframe was designed around conveying that much combined weight. But I see the logic in what you say. If the flight is under-sold and under weight, there will be provision for added fuel and range.

But I think it is pointless to give a maximum passenger aircraft performance range with less than a full complement of passengers, when the idea is to fill every seat. On their website, Airbus gives the range in terms of route service (Paris-BaAs). They include this disclaimer:

The data displayed refers to TYPICAL seating configurations and maximum range.

I assume that means with every seat occupied, and then fueled to MTOW. It lists A330-200 range as 6,750 nm with 253 seats filled.

I also suppose the RIF provision is built into the manufacturers legal range claims on applicable routes, thereby making BaAs to Paris with a full complement of pax legally possible only with an RIF option.

On the other hand, hold on a second: Are you talking about this AF flight in particular? I thought there was another thread for that and that this thread was to discuss RIF in general, where certainly what MCM says can be true regardless of whether it applied to this AF flight or not.

I only use AF447 here as an example because I already had that information from the other thread. Nothing here is specific to AF447, except that I am comparing the A330-200 range capability for BaAs to Paris with the fact that AF447 required an RIF option to fly a much shorter route (in the flight plan, in reality there was no need for the RIF option). And, according to Seatguru, their seating configuration is 219, 34 less than the AIrbus range specification. So that must be due to expected freight on board...?

[Gabriel]

I only use AF447 here as an example because I already had that information from the other thread. Nothing here is specific to AF447, except that I am comparing the A330-200 range capability for BaAs to Paris with the fact that AF447 required an RIF option to fly a much shorter route (in the flight plan, not in reality). So that must be due to freight on board...?

Based on this:

This takeoff weight broke down as follows:

 empty weight in operating condition: 126,010 kg,
 passenger weight: 17,615 kg (126 men, 82 women, 7 children and one baby(12)),
 weight in cargo compartment (freight and luggage): 18,732 kg,
 fuel weight: 70,400 kg.

In this case, probably yes. I can't imagine 17.6 t of passengers taking 18.7 t of luggage.

Say that every passenger (including the baby) takes 25 kg of luggge, you have 5.4 t of luggage, so you'd have about 13.3 t of cargo, that could have been used for fuel if there was enough room in the tanks (I don't know the capacity of the tanks).

In any event, yes, the fuel could have been increased if the payload (passengers or cargo) were reduced, as seen in the differences between plan 1 and plan 2 that were both at MTOW. Plan 2, with a reduced payload, didn't require a RIF.

And now what? Are you proposing to forbid the RIF if there is cargo that can be removed, but allow it if there only thing to remove is passengers or luggage?

I still don't see how AF is an example regarding what MCM said. It still can happen that, as MCM said, there are lots of flights where passengers would be left on the ground without the RIF.

What I would ask MCM is, if about 50% of the flights in Europe ar RIF, how is it that opting for the fuel stop is so rare? Bare luck? RIF used only where just barely a little more of fuel would have been needed to file without a RIF? Fuel reserves regulations exaggeratedly conservative, so even when not complied with (in the sense that it wouldn't be legal without a RIF) there is always much more fuel than needed?

[AJ]

Before the advent of the A80 and B744ER the route from LAX to MEL was often dispatched to a destination other than MEL.

In many cases this is because the tanks were full. Careful calculation of specific gravity still didn't allow a full KLAX-YMML flight plan.

Qantas designed a fuel policy, accepted by the regulator, that allowed long trans-Pacific flights in the 747SP. A fixed fuel reserve of 30 minutes (at 1500ft) is required at all times. To allow long sectors the 10% variable reserve is capped at 4,000kg for a B744.

If it wasn't capped a 14 hour flight would require 10% or 140,000kg of flight fuel, equating to another 14,000kg of fuel.....unrealistic!

A slight variance in the SG of the fuel would lead to differing amounts in full tanks (0.77SG = 166,616kg, 0.79SG = 170,948kg and 0.81SG = 175,275kg).

If full tanks weren't taken the tanker was often left hooked up until the last possible moment in case a ZFW drop allowed a top up!

Not to mention the fact that when planning the flight it is roughly 16 hours until landing to the weather forecasting for MEL is vague at best!

The rest of the fuel policy is complex and not worth listing but these are some of the variables facing the flight.

At flight planning you'd note that the flight had been planned to Nadi, Noumea, Brisbane or Sydney, especially if Melbourne had any weather holding requirements. A critical point had been calculated by the dispatchers where a decision would need to be made to allow a continuation of the flight towards Melbourne.

Nowadays the actually refile in flight is easy thanks to satellite communication and ACARS. The first few I did were via HF and a thick crayon. On one QF94 we had to refile three times thanks to varying weather conditions in Melbourne.

With that background do I think a RIF is a risk? No. At all times the flight carried sufficient fuel to proceed to a suitable airport. I understand why it is done. It is for commercial reasons but that is expected when flying for a commercial airline! Occasionally a tech stop is required, that is factored by the airline.

Working for an airline with extensive long haul experience leads to a good understanding of the overall need for RIF.

As for short haul operations; when the B717 started operating in Australia it had a very low MLW (cost saving), this meant that with a 60 minute weather holding requirement passengers were often left behind. Often you would see a Queen Air depart with the passengers bags after check-in closed! This problem was initially solved by using the RIF principle. Take Melbourne-Hobart as an example. If Launceston had no weather holding requirements the flight would dispatch for Launceston, re-evaluating Hobart in flight. With only inflight requirements to consider miraculously the flight could proceed to Hobart more often than not!

This was solved long term by paying Boeing more money for a higher MLW.

Whilst not a comprehensive answer that will give you a few more considerations in your debate.

[Evan]

Based on this:



In this case, probably yes. I can't imagine 17.6 t of passengers taking 18.7 t of luggage.

Say that every passenger (including the baby) takes 25 kg of luggge, you have 5.4 t of luggage, so you'd have about 13.3 t of cargo, that could have been used for fuel if there was enough room in the tanks (I don't know the capacity of the tanks).

That was the reality, I was referring to the flight plan estimates, which estimated either more luggage, more freight or fatter passengers (or more meat loaf and less pasta), and therefore included an RIF option. There were only 3 empty seats, so it wasn't less passengers.

The A330-200 can carry up to approx. 114t of fuel, but only 68t at MZFW. The ZFW was 6t under MZFW, but the TOW was just barely under MTOW (what is the difference between MRW and MTOW?). They took on about 2.5t added fuel over the MZFW maximum. So it seems that the fuel order was near the maximum allowable.

And now what? Are you proposing to forbid the RIF if there is cargo that can be removed, but allow it if there only thing to remove is passengers or luggage?

I would certainly want to forbid it if removal of freight eliminated the need for it. If certain long-range flights can't be legally flown without an RIF option even with only passengers and luggage, I would either say the flight requires an aircraft with longer range or a scheduled stopover. In other words, my solution is to match the equipment to the route instead of trying to extend the equipment performance in a way that relocated reserves to the ground and creates this potential for pressured risk decisions.

What I would ask MCM is, if about 50% of the flights in Europe ar RIF, how is it that opting for the fuel stop is so rare? Bare luck?

No, I understand that the odds of needing to make that stopover are very low. I'm talking about danger in rare instances though. When a weather situation similar to AF447 might reoccur, only this time the reserves aren't there and the pilots face a calculated, marginal decision, having to choose between marginal risk and guaranteed financial penalty. I mean, the rarity of a possible danger doesn't preclude us from trying to identify and eliminate it.

Look, I'm not sure that this is a practical suggestion, and I can see how it would burden the bottom line. But right now I feel pretty strongly that it is wise from a safety point of view, and that the risk is sufficient to justify it. It comes down to practicality vs safety, as it always does. The question is always where to place the point of balance.